The Diamondback moth (DBM) model was run with a biofix of May 15, 2020. DBM densities generally increase with increasing numbers of generations. Figure 1 represents the model output for the 2020 growing season (as of August 17, 2020). The number of generations varies from two in western Alberta to four in southeastern Saskatchewan and most of Manitoba (Fig. 1). Next, the model was run with climate normal data to compare the 2020 growing season with an ‘average’ growing season (Fig. 2). The second map (climate normal) indicates that an average growing season results in two to three generations, with a fourth generation predicted to occur near Winnipeg (Fig. 2). These results indicate that there was an elevated DBM risk in 2020.
Figure 1. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies as of August 17, 2020.Figure 2. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies as of August 17, 2020, using climate normal data.
The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Monitoring to apply the economic threshold: Remove the plants in an area measuring 0.1 m² (about 12″ square). Beat them on to a clean surface and count the number of larvae (Fig. 3) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 3. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.Figure 4. Diamondback moth pupa within silken cocoon.Figure 5. Diamondback moth.
Weekly Pheromone-baited Trapping Results – Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba(as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. For convenience, screen shots of the above maps or data have been placed below for Alberta, Saskatchewan, and Manitoba.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips: ● Some bertha armyworm larvae remain green or pale brown throughout their larval life. ● Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms. ● Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves. ● Larvae eat the outer green layer of the stems and pods exposing the white tissue. ● At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Figure 1. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
This week, the DBM model based on Harcourt (1954) was run with a biofix of May 15, 2020. Most of Alberta has had two generations. It is possible that three generations have been completed across Saskatchewan and southeastern Alberta where it has been warmer. Results indicate that a potential fourth generation may be occurring across southern Manitoba. DBM densities generally increase with increasing numbers of generations. Later maturing canola fields may be susceptible to damage resulting from larval feeding.
Figure 1. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies as of August 10, 2020.
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square). Beat them on to a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 2. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.Figure 3. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Model simulations for August 3, 2020, indicate that BAW development varies across the prairies. Figures 1 and 2 demonstrate that BAW populations near Winnipeg (Fig. 1) are more advanced than populations near Grande Prairie (Fig. 2). Populations near Winnipeg are predicted to be developing to pupae (Fig. 1). BAW populations near Grande Prairie are expected to be primarily in the larval stage (Fig. 2).
Figure 1. Predicted bertha armyworm (Mamestra configurata) phenology at Winnipeg MB as of August 3, 2020.Figure 2 Predicted bertha armyworm (Mamestra configurata) phenology at Grande Prairie AB as of August 3, 2020.
Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba(as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. For convenience, screen shots of the above maps or data have been placed below for Alberta, Saskatchewan, and Manitoba.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips: ● Some bertha armyworm larvae remain green or pale brown throughout their larval life. ● Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms. ● Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves. ● Larvae eat the outer green layer of the stems and pods exposing the white tissue. ● At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 4) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Figure 4. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Based on Harcourt (1954) the DBM model was run with a biofix of May 15, 2020. Model runs (as of August 3, 2020) were conducted with weather data for 2020 (Fig. 1) and climate normals (long term average temperatures). The first map illustrates that potentially three generations have been completed across Manitoba and southeastern Saskatchewan (Fig. 1). Most of the prairies have had two generations (Fig. 1). The second map, showing results for climate normal data, indicates that prairie populations should have completed two generations (Fig. 2).
Figure 1. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies as of August 3, 2020.Figure 2. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies using Climate Normal data.
The charts provide location specific details regarding potential development at Winnipeg (Fig. 3) and Lacombe (Fig. 4). The first chart illustrates DBM development at Winnipeg. Results indicate that there is potential for a fourth generation of DBM to occur in southern Manitoba. Populations near Lacombe are predicted to be completing the second generation.
Figure 3. Predicted diamondback moth (Plutella xylostella) phenology at Saskatoon SK. Values are based on model simulations (April 1-August 3, 2020).Figure 4. Predicted diamondback moth (Plutella xylostella) phenology at Lacombe AB. Values are based on model simulations (April 1-August 3, 2020).
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square). Beat them on to a clean surface and count the number of larvae (Fig. 5) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 5. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.Figure 6. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Thrips in canola (Thynsanoptera) – While scouting at this time of year, curled canola pods may be encountered. The culprits are quite possibly thrips.
Figure 1. Thrips damage observed in canola in the northeast of Saskatchewan in July 2016 (Photo: AAFC-Saskatoon, Olfert 2016).
Damage: Flower thrips (Thysanoptera) are pests of a broad range of plants including cereals and broadleaved crops such as canola. Thrips are minute, slender-bodied insects with rasping-sucking mouthparts and feed by rasping the surface of canola buds and sucking up plant fluids.
Biology: Thrips have six life stages: egg, two larval stages, a prepupal and pupal stage and an adult. Both adults and nymphs cause damage by feeding on the flower and buds. Limited surveys in 1999 in Saskatchewan and Alberta indicated that the predominant species were Frankliniella tritici (flower thrip) followed by Thrips tabaci (onion thrip) and T. vulgatissimus (no common name).
In canola, pods damaged by thrips are often curled and tend to drop prematurely. Some species, such as T. vulgatissimus have been credited with contributing to pollination.
Read more about thrips in canola by accessing this article by Olfert et al. 1998).
Ladybird beetle larvae (Fig. 1), pupae (Fig. 2), and adults (Fig. 3) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids.
Figure 4. An aphid “mummy” adhered to a wheat awn. A “mummy” is the aphid host transformed to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge).
Click to link to last week’s information posted for Wk 13 (released 23Jul2020) to review the predictive model outputs for this insect pest. As larvae now begin to develop and feed in fields, emphasis is now placed on in-field scouting in areas where high moth counts are being intercepted by provincial networks highlighted below.
Weekly Pheromone-baited Trapping Results– Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba. Remember in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. For convenience, screen shots of available maps or data from Alberta, Saskatchewan, and Manitoba are below.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images above (Fig. 4) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Figure 4. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Diamondback moth (Plutellidae: Plutella xylostella) – Once the diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Monitoring:Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.Figure 2. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3).
Figure 3. Sequential sampling for lygus bugs at late flowering stage in canola.
If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Model simulations for July 19, 2020 (Fig. 1) indicate that 23% of the bertha armyworm (BAW) population is in the egg stage (compared to 35% last week) and 77% are predicted to be larvae (compared to 65% last week). Across the Parkland and Peace River regions, BAW populations are predicted to be primarily in the egg stage (Fig. 1). Other than the Peace River region, populations are primarily in the larval stage (Fig. 1). Fields near Carman, Winnipeg and Morden in Manitoba are expected to have first appearance of pupae, suggesting larval development is advanced (Fig. 1).
Figure 1. Predicted percent of bertha armyworm (Mamestra configurata) population in the larval stageas of July 19, 2020.
The two graphs below demonstrate that BAW populations near Winnipeg (Fig. 2) are more advanced than populations near Grande Prairie (Fig. 3). In Winnipeg populations are primarily in the larval stage with first appearance of pupae (Fig. 2). BAW populations near Grande Prairie are predicted to be in adult, egg and larval stages (Fig. 3).
Figure 2. Predicted bertha armyworm (Mamestra configurata) phenology at Winnipeg MB as of July 19, 2020.Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Grande Prairie AB as of July 19, 2020.
Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba(as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. For convenience, screen shots of the above maps or data have been placed below for Alberta, Saskatchewan, and Manitoba.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images above (Fig. 4) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Figure 4. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3).
Figure 3. Sequential sampling for lygus bugs at late flowering stage in canola.
If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Model simulations for July 12, 2020 indicate that 35% of the population is in the egg stage (37% last week) and 65% of the population is in the larval stages (14% last week). Across the Parkland and Peace River regions, BAW populations are predicted to be primarily in the egg stage (Fig. 1). Populations across southern regions are primarily in the larval stage (Fig. 1).
Figure 1. Predicted percent of bertha armyworm (Mamestra configurata) population in the larval stageas of July 12, 2020.
The two graphs below demonstrate that larval development near Brandon is predicted to be ahead of fields near Grande Prairie. In Brandon, populations are primarily in the larval stage (Fig. 2) while BAW populations near Grande Prairie are predicted to be predominantly in adult and egg stages (Fig. 3).
Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Brandon MB as of July 12, 2020.Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Grande Prairie AB as of July 12, 2020.Figure 5. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba(as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is how the economic threshold is applied to manage this pest.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images above (Fig. 5) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3).
Figure 3. Sequential sampling for lygus bugs at late flowering stage in canola.
If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Model simulations for July 5, 2020, indicate that 5 % of the population is in the pupal stage (26 % last week), 43 % is in the adult stage (52 % last week), and 37 % of the population is in the egg stage (20 % last week). In southern Manitoba and southeastern Saskatchewan, larval stages are predicted to increase this week (14 % compared to 2 % last week). Across the Parkland and Peace River regions, BAW populations are predicted to be mostly adults with oviposition occurring in these areas (Fig. 1). Operation of BAW traps in these areas should continue until adult emergence is complete. Populations across southern regions are primarily in the larval stage (Fig. 2).
Figure 1. Predicted percent of bertha armyworm (Mamestra configurata) population in the adult stageas of July 5, 2020.Figure 2. Predicted percent of bertha armyworm (Mamestra configurata) population in the larval stageas of July 5, 2020.
The two graphs demonstrate that larval development near Brandon (Fig. 3) is predicted to be ahead of fields near Lethbridge (Fig. 4).
Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Brandon MB as of July 5, 2020.Figure 4. Predicted bertha armyworm (Mamestra configurata) phenology at Lethbridge AB as of July 5, 2020.Figure 5. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).
Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba(as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is how the economic threshold is applied to manage this pest.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images above (Fig. 5) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Once diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Wind Trajectory Updates – Completed for 2020 growing season as of Week 09 (released June 22, 2020).
Weekly Pheromone-baited Trapping Results – Early season detection of diamondback moth is improved through the use of pheromone-baited delta traps deployed in fields across the Canadian prairies. Click each province to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba as they become available. Check these sites to assess cumulative counts and relative risk in your geographic region.
Monitoring:Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8 mm long.Note brown head capsule and forked appearance of prolegs on posterior.
Figure 2. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Reminder – Field scouting is critical – it enables the identification of potential risks to crops. Accurate identification of insect pests PLUS the application of established monitoring methods will enable growers to make informed pest management decisions.
We offer TWO generalized insect pest scouting charts to aid in-field scouting on the Canadian prairies:
Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to outbreaking insect pest species.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 07Aug2019), and Manitoba (locate table on pg 6). Regions in all three prairie provinces are reporting “uncertain” risk based on pheromone-baited unitrap cumulative counts. SCOUT NOW to confirm in-field larval counts and REMEMBER that LARVAL DENSITIES CAN VARY DRAMATICALLY even between adjacent fields! Scout to protect @FieldHeroes and avoid economic losses! Use the Field Heroes’ scouting guide for bertha armyworm and be sure to read more at their website! Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Albertaand the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify egg masses and the economically important larvae in canola.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada).
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Bertha armyworm (Lepidoptera: Mamestra configurata) – Important – Watch for updates from your local provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 31Jul2019), and Manitoba (locate table on pg 6). Regions in all three prairie provinces are reporting “uncertain” risk based on pheromone-baited unitrap cumulative counts.
SCOUT NOW to confirm in-field larval counts and REMEMBER that LARVAL DENSITIES CAN VARY DRAMATICALLY even between adjacent fields! Scout to protect @FieldHeroes and avoid economic losses! Use the Field Heroes’ scouting guide for bertha armyworm and be sure to read more at their website!
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify egg masses and the economically important larvae in canola.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Lygus bugs (Lygus spp.) – Reminder – The Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids! Both posts include tips to to discern the difference between when doing in-field scouting!
The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Predictive model updates are completed for the growing season but can be reviewed here (Wk 14).
Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 24Jul2019), and Manitoba (locate table on pg 6). regions in all three prairie provinces are reporting “uncertain” risk based on pheromone-baited unitrap cumulative counts.
This week – SCOUT NOW to confirm in-field larval counts and REMEMBER that LARVAL DENSITIES CAN VARY DRAMATICALLY even between adjacent fields! Scout to protect @FieldHeroes and avoid economic losses! Use the Field Heroes’ scouting guide for bertha armyworm and be sure to read more at their website!
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify egg masses and the economically important larvae in canola.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Reminder – One last time for this growing season….. We have updated the field scouting charts so they now link to pages within the 2018 version of the Insect Field Guide.
We offer TWO generalized insect pest scouting charts to aid in-field scouting on the Canadian prairies:
Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to insect pest species but they rely on in-field scouting!
Bertha armyworm (Lepidoptera: Mamestra configurata) – Predictive model updates are completed for the growing season but can be reviewed here (Wk 14).
Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 10Jul2019), and Manitoba (look on pg 8).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify egg masses and the economically important larvae in canola.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Predictive model updates are completed for the growing season but can be reviewed here (Wk 14).
Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 10Jul2019), and Manitoba (look on pg 7).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 3) to help identify egg masses and the economically important larvae in canola.
Figure 3. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Lygus bugs (Lygus spp.) – The Insect of the Week’s doppelganger is the lygus bug versus the alfalfa plant bug. It includes tips to to discern the difference between these plant bug complexes when doing in-field scouting!
The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report in-field CSPW scouting data then check the online map posted by Alberta Agriculture and Forestry (screenshot retrieved 18Jul2019 provided below as reference).
Diamondback moth (Plutellidae: Plutella xylostella) – Once diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
Figure 2. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Bertha armyworm (Lepidoptera: Mamestra configurata) – Early instar bertha armyworm are predicted to begin appearing across the prairies. A model run for Saskatoon SK indicates that the hatch should be complete (Fig.1) and that BAW should be in the early instar (Fig. 2).
Figure 1. Predicted status of bertha armyworm (Mamestra configurata) populations as of July 8, 2019. Figure 2. Predicted percent of bertha armyworm (Mamestra configurata) populations at LARVAL STAGE across the Canadian prairies as of July 8 2019.
Important – Watch your provincial monitoring networks who are weekly recording cumulative pheromone-baited traps in Alberta, Saskatchewan, and Manitoba (pg 8).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 3) to help identify egg masses and the economically important larvae in canola.
Figure 3. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Diamondback moth (Plutellidae: Plutella xylostella) – Once the diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
Figure 2. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Bertha armyworm (Lepidoptera: Mamestra configurata) – Last week (Fig. 1), bertha armyworm adults were emerging across the prairies and oviposition began across most of the southern prairie regions of SK, AB and MB. That means it’s time to start check the undersides of canola leaves for egg masses and newly hatched larvae!
Figure 1. Predicted precent of bertha armyworm (Mamestra configurata) populations at EGG STAGE across the Canadian prairies as of June 24 2019.
Here’s where bertha armyworm moths were intercepted last year (Fig. 2) so areas previously highlighted in yellow, gold, orange or red should be on the lookout in 2019 for larvae. Also watch your provincial monitoring networks who are weekly recording cumulative pheromone-baited traps in Alberta, Saskatchewan (table on Left of webpage), and Manitoba (pg 7).
Figure 2. Cumulative moth counts from pheromone-baited unitraps deployed during the 2018 growing season.
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Again, thanks to John Gavloski (Manitoba Agriculture) who helped update the PPMN Bertha armyworm monitoring protocol. Use the images below (Fig. 3) to help identify moths from the by-catch that will be retained in phermone-baited unitraps.
Figure 3. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Also be sure to review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Bertha armyworm (Lepidoptera: Mamestra configurata) – Bertha armyworm adults should be emerging across the prairies and oviposition is predicted to have begun across most of the southern prairie regions of SK, AB and MB (Fig. 1).
Figure 1. Predicted precent of bertha armyworm (Mamestra configurata) populations at EGG STAGE across the Canadian prairies as of June 24 2019.
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Again, thanks to John Gavloski (Manitoba Agriculture) who helped update the PPMN Bertha armyworm monitoring protocol. Use the images below (Fig. 2) to help identify moths from the by-catch that will be retained in phermone-baited unitraps.
Figure 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Also be sure to review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pupal development is progressing and this week adults should be occurring across most of southern SK and localized areas in AB. Most of the population is predicted to be in the pupal stage (89%). The BAW model indicates that 10% of the population is in the adult stage .
Figure 1. Predicted precent of bertha armyworm (Mamestra configurata) populations at adults stage across the Canadian prairies as of June 17, 2019.
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Again, thanks to John Gavloski (Manitoba Agriculture) who helped update the PPMN Bertha armyworm monitoring protocol. Use the images below (Fig. 2) to help identify moths from the by-catch that will be retained in phermone-baited unitraps.
Figure 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Also be sure to review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 02Jul2019).
Bertha armyworm (Lepidoptera: Mamestra configurata) – Based on BAW model runs, this week pupal development is greater than 80% across most of southern and central areas of the prairies (Fig. 1). Within the next five days BAW adults should begin to emerge in these areas.
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development across the Canadian prairies as of June 11, 2019.
Please ensure pheromone traps are out in SK and AB fields this week!
Table 1. Predicted emergence date of bertha armyworm moths at select locations across the Canadian prairies in 2019.
A special thanks to John Gavloski (Manitoba Agriculture) who helped update the PPMN Bertha armyworm monitoring protocol. Use the images below (Fig. 2) to help identify moths from the by-catch that will be retained in phermone-baited unitraps.
Figure 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Also be sure to review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches. Monitoring should typically begin for this pest as canola enters the bud stage.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
The case of the bertha armyworm and the clover cutworm (and other cutworm species)
Clover cutworm larva cc-by 3.0 Lo Troisfontaine
Bertha armyworm – caterpillar Mike Dolinski, MikeDolinski@hotmail.com
Are those bertha armyworms (Mamestra configurata) eating your canola, mustard or alfalfa (also found on lamb’s-quarters, peas, flax, potato)? Or is it maybe a clover cutworm (Discestra trifolii)? [Note: not all cutworm species spend their larval stage underground.] The larvae of the two species are doppelgangers as they are similar in appearance, have a large overlap in host crops, and have similar timing (June-September). Telling them apart can be a challenge but here are few tips to focus on to help distinguish:
Colour:
there are generally fewer velvety black clover cutworm caterpillars, with most of the clover cutworm larvae being green or pale brown
Lateral stripe:
On the clover cutworm it is yellowish-pink
On the bertha armyworm it is yellowish-orange
Climbing cutworm larva – from Cutworm Field Guide Climbing cutworm adults – from Cutworm Field Guide
In terms of scouting, economic thresholds and control options, treat both species as you would bertha armyworms.
Bertha armyworm – adult Alberta Agriculture and Rural Development Clover cutworm adult cc-by-nc-sa 2.0 Ilona Loser
Bertha armyworm (Lepidoptera: Mamestra configurata) – Based on BAW model runs, pupal development is nearing 80% in some areas of southern and central AB and SK (Fig. 1). BAW adults may begin to emerge within the next 10 days (Table 1).It is advisable to place pheromone traps in fields when pupal development is 80% to capture the full extent of adult flight activity. Based on this value, traps should be put out in SK and AB fields this week.
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development acrossthe Canadian prairies as of June 3, 2019.
Table 1. Predicted emergence date of bertha armyworm moths at select locations across the Canadian prairies in 2019.
Recent warm conditions have advanced bertha armyworm (BAW) pupal development. Compared to last week, development is 2-6 days faster and development is 2 days ahead of normal (based on climate normals). Model outputs were run for bertha armyworm for Saskatoon SK (Fig. 2), Lethbridge AB (Fig. 3), and Edmonton AB (Fig. 4).
Figure 2. Predicted development of bertha armyworm populations near Saskatoon SK as of June 3, 2019. Figure 3. Predicted development of bertha armyworm populations near Lethbridge AB as of June 3, 2019. Figure 4. Predicted development of bertha armyworm populations near Edmonton AB as of June 3, 2019.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pupal development is approximately 40%. Average development is 48% (Fig. 1).
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development acrossthe Canadian prairies as of May 28, 2019.
In order to determine when adults may emerge, the BAW model was run for Brandon MB (Fig. 2), Saskatoon SK (Fig. 3), Lethbridge AB (Fig. 4) and Edmonton AB (Fig. 5) and projected to June 30, 2019. Model projections indicate that adults will begin to emerge in mid June. Recent heat will advance development of pupae. Traps should be placed in fields when pupal development reaches 80%. Based on model projections, it is advisable that traps be placed in fields on or before June 7.
Figure 2. Predicted development of bertha armyworm populations near Brandon MB projected to June 30, 2019. Figure 3. Predicted development of bertha armyworm populations near Saskatoon SK projected to June 30, 2019. Figure 4. Predicted development of bertha armyworm populations near Lethbridge AB projected to June 30, 2019. Figure 5. Predicted development of bertha armyworm populations near Edmonton AB projected to June 30, 2019.
Flea Beetles (Chrysomelidae: Phyllotreta species)– As newly seeded stands begin to emerge, the need for in-field scouting increases. Review Wk05 for flea beetle information, visual guides to help estimate percent of cotyledon damage, and links to the Insect Field Guide.
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to outbreaking insect pest species.
Flea Beetles (Chrysomelidae: Phyllotreta species)– Reminder – Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Canola Watch circulated this article but also use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) – take it scouting!
Figure 1. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).
Figure 2. Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).
Refer to the flea beetle page from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.
Flea Beetles (Chrysomelidae: Phyllotreta species) – Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Canola Watch circulated this article but also use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) – take it scouting!
Figure 1. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).
Figure 2. Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).
Refer to the flea beetle page from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.
Field scouting is critical – it enables the identification of potential risks to crops. Accurate identification of insect pests PLUS the application of established monitoring methods will enable growers to make informed pest management decisions.
We offer TWO generalized insect pest scouting charts to aid in-field scouting on the Canadian prairies:
Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to outbreaking insect pest species.
In 2018, swede midge pheromone traps were deployed at 41 sites across the Prairie region of Canada to monitor adult populations of this brassica pest. Of the 41 trap sites, 16 were located in Alberta, 19 in Saskatchewan (where positive swede midge identifications were made in 2007 and 2009), and 6 in Manitoba.
None of the traps were positive for swede midge in 2018.
We are grateful to all of the producers, agronomists, and cooperators who participated in the 2018 swede midge monitoring project. Without your assistance, we could not have supported such a thorough and widespread pheromone monitoring program.
We also extend our thanks to Jonathon Williams for organizing the program, distributing trapping materials, and processing returned sticky cards for adult swede midge.
Because of the serious threat that swede midge poses to canola production, it is vital that monitoring for swede midge continues across the Prairies. At this time, plans are being made for the 2019 swede midge monitoring program. We hope that we can count on your support and cooperation in 2019.
At this time, plans are being made for the 2019 swede midge monitoring program. Agrologists or growers interested in performing weekly monitoring in 2019 are encouraged to contact Jonathon Williams, Boyd Mori, or Meghan Vankosky for more information.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pheromone trapping across the prairies is almost complete for the 2018 growing season but now it is important to scout for larvae feeding on leaves and developing pods!
Review your province’s 2018 bertha armyworm pheromone trapping results towards the end of this Post.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Albertans can access the online reporting map (screenshot below retrieved 14Aug2018 for reference):
Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 01Aug2018 for reference):
Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates. A screen shot of that summary (retrieved 01Aug2018) is pasted below:
Lygus bugs (Lygus spp.) – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind:
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Thrips in canola (Thynsanoptera) – While scouting at this time of year, curled canola pods may be encountered. The culprits are quite possibly thrips.
Thrips damage observed in canola in the northeast of Saskatchewan in July 2016 (Photo: AAFC-Saskatoon, Olfert 2016).
Damage: Flower thrips (Thysanoptera) are pests of a broad range of plants including cereals and broadleaved crops such as canola. Thrips are minute, slender-bodied insects with rasping-sucking mouthparts and feed by rasping the surface of canola buds and sucking up plant fluids.
Biology: Thrips have six life stages: egg, two larval stages, a prepupal and pupal stage and an adult. Both adults and nymphs cause damage by feeding on the flower and buds. Limited surveys in 1999 in Saskatchewan and Alberta indicated that the predominant species were Frankliniella tritici (flower thrip) followed by Thrips tabaci (onion thrip) and T. vulgatissimus (no common name).
In canola, pods damaged by thrips are often curled and tend to drop prematurely. Some species, such as T. vulgatissimus have been credited with contributing to pollination.
Curled pods of canola caused by thrips feeding damage (Photos: AAFC-Saskatoon, Olfert et al. 1998)
Read more about thrips in canola by accessing this article by Olfert et al. 1998).
Flea Beetles (Chrysomelidae: Phyllotreta species) – By early pod stages in canola, newly eclosed adult flea beetles begin to emerge from the soil. These individuals typically feed then move away from canola fields to locate overwintering habitats.
Normally, it can be difficult to locate these newly emerged adults but every few years they are easily observed among canola pods. These adults can feed on upper leaves and nip at the exterior of canola pods but are typically observed in low densities – too low to cause economic damage. Even so, be watchful – areas with high numbers of flea beetles late in the growing season are worthwhile to scout early in 2019.
Remember – the Action Threshold for flea beetles on canola is 25% of COTYLEDON LEAF AREA consumed.
Normally, it is NOT recommended to apply foliar insecticides for flea beetles in canola during the pod stages for the following reasons:
Flea beetles are very mobile at this point in the season,
Canola canopy is very thick,
Growers must be cautious about pre-harvest intervals,
PLUS, little is understood about overwintering survival of this pest!
Reminder – Earlier this season, the Insect of the Week featured flea beetles!
Refer to the flea beetle page from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.
Reminder – While scouting, you may encounter these fascinating organisms…..
Figure 1. Ladybird beetle larva (photo credit: AAFC-Beaverlodge)Figure 2. Ladybird beetle pupa (Left) and larva (Right) (photo credit: AAFC-Beaverlodge)Figure 3. Ladybird beetle pupa (photo credit: AAFC-Beaverlodge)Figure 4. Ladybird beetle (Coccinella septempunctata) (photo credit: AAFC-Beaverlodge)Figure 5. Aphids nestled on wheat head (photo credit: AAFC-Beaverlodge)Figure 6. An aphid “mummy” adhered to a wheat awn. Mummy is the aphid host converted to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge)
Ladybird beetle larvae (Fig. 1-2), pupae (Fig. 2-3), and adults (Fig. 4) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids (Fig. 5).
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pheromone trapping across the prairies is almost complete for the 2018 growing season but now it is important to scout for larvae feeding on leaves and developing pods!
Review your province’s 2018 bertha armyworm pheromone trapping results towards the end of this Post.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Albertans can access the online reporting map (screenshot below retrieved 31Jul2018 for reference):
Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 31Jul2018 for reference):
Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates. A screen shot of that summary is pasted below:
Thrips in canola (Thynsanoptera) – While scouting at this time of year, curled canola pods may be encountered. The culprits are quite possibly thrips.
Thrips damage observed in canola in the northeast of Saskatchewan in July 2016 (Photo: AAFC-Saskatoon, Olfert 2016).
Damage: Flower thrips (Thysanoptera) are pests of a broad range of plants including cereals and broadleaved crops such as canola. Thrips are minute, slender-bodied insects with rasping-sucking mouthparts and feed by rasping the surface of canola buds and sucking up plant fluids.
Biology: Thrips have six life stages: egg, two larval stages, a prepupal and pupal stage and an adult. Both adults and nymphs cause damage by feeding on the flower and buds. Limited surveys in 1999 in Saskatchewan and Alberta indicated that the predominant species were Frankliniella tritici (flower thrip) followed by Thrips tabaci (onion thrip) and T. vulgatissimus (no common name).
In canola, pods damaged by thrips are often curled and tend to drop prematurely. Some species, such as T. vulgatissimus have been credited with contributing to pollination.
Curled pods of canola caused by thrips feeding damage (Photos: AAFC-Saskatoon, Olfert et al. 1998)
Read more about thrips in canola by accessing this article by Olfert et al. 1998).
Lygus bugs (Lygus spp.) – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind:
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 31Jul2018).
While scouting, you may encounter these fascinating organisms…..
Figure 1. Ladybird beetle larva (photo credit: AAFC-Beaverlodge)Figure 2. Ladybird beetle pupa (Left) and larva (Right) (photo credit: AAFC-Beaverlodge)Figure 3. Ladybird beetle pupa (photo credit: AAFC-Beaverlodge)Figure 4. Ladybird beetle (Coccinella septempunctata) (photo credit: AAFC-Beaverlodge)Figure 5. Aphids nestled on wheat head (photo credit: AAFC-Beaverlodge)Figure 6. An aphid “mummy” adhered to a wheat awn. Mummy is the aphid host converted to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge)
Ladybird beetle larvae (Fig. 1-2), pupae (Fig. 2-3), and adults (Fig. 4) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids (Fig. 5).
This week’s Insects of the Week are two parasitoid wasps, an Inostemma sp. (Hymenoptera: Platygastridae) and a Gastrancistus sp. (Hymenoptera: Pteromalidae). These parasitoids are natural enemies of the canola flower midge (Contariniabrassicola, Diptera: Cecidomyiidae), a newly discovered fly species that uses canola as its host plant. The parasitoids have been found throughout the Prairies emerging from infested galls created by the canola flower midge. Little is known about these two species, but parasitism rates as high as 30% have been noted in northeast Saskatchewan.
Lygus bugs (Lygus spp.) – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind:
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Sampling becomes more representative IF repeated at multiple spots within a field. For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C).
If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pheromone trapping across the prairies is almost complete for the 2018 growing season but now it is important to scout for larvae feeding on leaves and developing pods.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Albertans can access the online reporting map (screenshot below retrieved 24Jul2018 for reference):
Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 26Jul2018 for reference):
Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates. The July 25th update summarized that, “out of the 99 traps, 87 currently have cumulative counts in the low risk category (less than 300), one trap is in the moderate risk range, and 11 traps are in the uncertain risk category. Most of the highest cumulative counts so far are in the western part of Manitoba.”
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 24Jul2018).
This week’s Insect of the week is a new find on the prairies, tentatively called the canola flower midge, Contarinia brassicola (Diptera: Cecidomyiidae). The canola flower midge has been found throughout central Alberta, Saskatchewan, and the Swan River Valley in Manitoba. The female lays eggs on developing canola flower buds. Upon hatching, the larvae feed within the developing flower and cause the formation of a “pop-bottle”-shaped gall. To date, this is the only damage associated with the midge, and it has been minimal across the prairies.
Adult canola flower midges appear similar to swede midge (Contarinia nasturtii). They are tiny, delicate flies, 2-5 mm in size. They can be differentiated from swede midge based on the appearance of the female antennae, the damage symptoms they produce and genetically.
Many thanks to Scott Meers and Shelley Barkley (Alberta Agriculture and Forestry) for organizing the Alberta surveys for the canola flower midge.
Lygus bugs (Lygus spp.) – As of July 16, 2018, the model output indicates that Lygus populations range from first instar stage to adults with most populations being comprised mainly of fifth instar stage and adult stages (Fig. 1).
Figure 1. Lygus development (average instar) based on model simulations, for April 1 – July 16, 2018.
Warmer temperatures have resulted in more rapid development in southern Manitoba and southeast Saskatchewan. Model runs were conducted for Saskatoon, Lethbridge and Grande Prairie to compare site specific development. The Lygus model output suggests that populations in Lethbridge and Saskatoon should be primarily comprised of fifth instar and adult stages while populations near Grande Prairie are predicted to be comprised of fourth and fifth instar stages with adults beginning to appear (Fig. 2)
Figure 2. Predicted Lygus phenology at Saskatoon, Lethbridge and Grande Prairie. Values are based on model simulations, for April 1 – July 16, 2018.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Cabbage root maggot (Delia spp.) – Among root feeding pests of canola, historically five species of Delia flies have been identified across the Canadian prairies. Delia radicum (L.), D. floralis (Fallén), D. platura (Meigan), D. planipalpis (Stein), and D. florilega (Zett.) have been observed in canola over 30 years of research (Liu and Butts 1982, Griffiths 1986a, Broatch and Vernon 1997; Soroka and Dosdall 2011). A summary of root maggot biology, research, and pest management recommendations for canola production was published by Soroka and Dosdall (2011).
Root maggots continue to be a problematic in canola production largely owing to the fact that (i) the species is composition varies by geographic latitude and local conditions, plus (ii) one or two generations per year will occur but varies by species. The species complex is typically characterized by multiple, overlapping generations of Delia resulting in adults laying eggs in canola (Refer to upper left photo for adult and eggs) from late Spring to October and maggots feeding on roots from late rosette until late fall (Refer to upper right photo). Root maggots pupate and overwinter within cigar-shaped, reddish-brown puparia 5-20 cm below the soil surface (Soroka and Dosdall 2011) so canola-on-canola rotations should be avoided. In the spring, adults emerge from mid-May to mate and females lay oval, white eggs singly or in batches near the base of cruciferous host plants over a 5-6 week period. The larvae develop through three instar stages which feed on root hairs then secondary roots initially whereas older maggots will feed into the taproot of a canola plant.
Refer to the root maggotpages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Bertha armyworm (Lepidoptera: Mamestra configurata) – Pheromone trapping across the prairies is almost complete for the 2018 growing season but now it is important to scout for larvae feeding on leaves.
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Albertans can access the online reporting map (screenshot below retrieved 18Jul2018 for reference):
Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 18Jul2018 for reference):
Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates. The July 11th update summarized that, “out of the 99 traps, 93 currently have cumulative counts in the low risk category (less than 300), and six traps are in the uncertain risk category. Most of the highest cumulative counts so far are in the western part of Manitoba. Trap counts in eastern Manitoba and the Interlake have generally been quite low.”
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 18Jul2018).
Lygus bugs (Lygus spp.) – Due to warmer temperature data, the Lygus model output has predicted rapid a increase in development across southern and central prairie regions with Lygus adults forecast to occur across most of this area (Fig. 1).
Figure 1. Lygus development (average instar) based on model simulations, for April 1 – July 9, 2018.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
The cabbage seedpod weevil is a chronic pest of canola in southern Alberta and south western Saskatchewan; it has recently reached Manitoba as well. The pest is managed with insecticides, which are sprayed at early flower. This year, in some canola fields around Lethbridge AB, an abundant parasitoid wasp was noticed at the time when fields may be sprayed. The wasp was identified as Diolcogaster claritibia (Fig. 1; thanks to Vincent Hervet and Jose Fernandez for confirming identification).
The wasp is a parasitoid that attacks diamondback moth larvae and recently abundant in some fields in 2017. In some of the fields sampled, as many parasitoids as cabbage seedpod weevil (i.e., nearly one per sweep) were observed. In the fields sampled (i.e., around 10), cabbage seedpod weevils were below thresholds on average, though some spots may have been close to the threshold of 2-3 weevils per sweep.
The above observation emphasizes the value of beneficial arthropods like Diolcogaster claritibia. It is important to recognize that foliar applications of insecticides kill beneficial insects like this small wasp (about 2 mm) which attacks and helps regulate pest populations of diamondback moth or other Lepidoptera, including cutworms and cabbage worms. Thus, think beneficials before you spray!
Figure 1. Diolcagaster claritibia adult measuring ~2mm in length (Photo credit J. Fernandez, AAFC-Ottawa).
Bertha armyworm (Lepidoptera: Mamestra configurata) – BAW populations are predicted to be in the larval stages and may have begun feeding within the plant canopy on leaves. Figure 1 illustrates that BAW oviposition is complete and that the population is in the larval stage for populations near Brandon (Fig. 1).
Figure 1. Predicted BAW phenoloyg at Brandon MB. Values are based on model simulations for April 1-July 2, 2018 (projected to July 10, 2018)
Many thanks to those who are checking a bertha armyworm pheromone trap on a weekly basis. Please use the reference photo below kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions. Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths. Check carefully and thanks for your help!
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Keep track of the Provincial Entomologist Updates for the latest in-season pheromone trap monitoring results for 2018.
Saskatchewanians can view the latest pheromone trap interceptions below kindly provided by Saskatchewan Agriculture.
Albertans can access the online reporting map (screenshot retrieved 04Jul018 provided below for reference:
Lygus bugs (Lygus spp.) – As of July 2, 2018, the model indicates the Lygus populations range from the 1st instar stage to adults with most of the population being at the 4th and 5th instar stages (Fig. 1). Warmer temperatures have resulted in rapid development in southern Manitoba and southeast Saskatchewan.
Figure 1. Predicted Lygus development (average instar stage) based on model simulations for April 1-July 2, 2018.
This week, model runs were conducted for Saskatoon, Lethbridge and Grande Prairie to compare site specific development. The Lygus model output suggests that Saskatoon populations should be primarily be in the 3-5th instar stages (Fig. 2) with development predicted to be marginally slower in Lethbridge (Fig. 3). Populations near Grande Prairie are predicted to be in the 3rd instar stage (Fig. 4).
Figure 2. Predicted Lygus phenology for April 1-July 2, 2018, for Saskatoon SK.Figure 3. Predicted Lygus phenology for April 1-July 2, 2018, for Grande Prairie AB.Figure 4. Predicted Lygus phenology for April 1-July 2, 2018, for Lethbridge AB.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
The insect of the week is the Bruner grasshopper (Melanoplus bruneri). Observed since the 1920s in Canada, this species is a relatively recent addition to the list of grasshopper pest species occurring in crop production areas. Previously, it was not considered a crop pest.
It is a medium-sized grasshopper (males 18-22 mm; females 22-27 mm) with dark and often reddish colour tones. It is similar in appearance and size to the migratory grasshopper (Melanoplus sanguinipes) but is distinguished by differences in the male genitalia. The Bruner grasshopper has recently become the predominant grasshopper species in many northern crop production areas of Alberta and parts of Saskatchewan. It occupies a wide geographic range and is found throughout much of Canada and the United States.
The Bruner grasshopper feeds mainly on broadleaf host plants but the species can feed upon several species of grasses. It has been observed in high numbers feeding in pulse crops, canola, and cereals.
Researchers are investigating if this species follows a two-year life cycle (i.e. do eggs require exposure to two winters before hatching?) in the Peace River region and parts of central Alberta.
Bertha armyworm (Lepidoptera: Mamestra configurata) – As of June 24, 2018, BAW development continues to be 7-10 days ahead of normal development (Figs. 3 A and B). Pupal development is complete across the prairies (Fig. 1).
Near Saskatoon SK, BAW egg hatch is nearly complete and larvae are present (Fig. 2). Based on Long Term Climate Normal (LTCN) data, larvae generally begin to occur the last few days of June (Fig. 3).
Figure 2. Predicted BAW phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 24, 2018 and B) Long term climate normals.Figure 3. Predicted BAW phenology at Saskatoon SK. Values are based on model simulations for Long Term Climate Normals (LTCN).
Many thanks to those who are checking a bertha armyworm pheromone trap on a weekly basis. Please use the reference photo below kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions. Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths. Check carefully and thanks for your help!
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Keep track of the Provincial Entomologist Updates for the latest in-season pheromone trap monitoring results for 2018.
Albertans can access the online reporting map (screenshot retrieved 28Jun2018 provided below for reference:
Lygus bugs (Lygus spp.) – As of June 24, 2018, the Lygus model suggests that Saskatoon populations should consist of mostly 4th instar nymphs (Fig. 1). Predicted development for the 2018 growing season is greater than for development that is based on long term climate normals (Fig. 2).
Figure 1. Predicted Lygus phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 24, 2018.Figure 2. Predicted Lygus phenology at Saskatoon SK. Values are based on model simulations for Long Term Climate Normals.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.
Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.
Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.
Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.
Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.
Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring:
Begin sampling when the crop first enters the bud stage and continue through the flowering.
Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.
Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.
Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.
An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts).
Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.
High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.
There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot is provided below for reference; retrieved 28Jun2018).
Bertha armyworm (Lepidoptera: Mamestra configurata) – BAW development continues to be 7-10 days ahead of normal development (Figs. 1 and 2). Near Saskatoon, oviposition is predicted to be well underway (Fig. 1).
Figure 1. Predicted bertha armyworm phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 18, 2018.
Based on climate data (LTCN), oviposition near Saskatoon should begin the third week of June (Fig. 2).
Figure 2. Predicted bertha armyworm phenology at Saskatoon SK when using Long Term Climate Normal (LTCN) data.
Many thanks to those who are checking a bertha armyworm pheromone trap on a weekly basis. Please use the reference photo below kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions. Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths. Check carefully and thanks for your help!
Monitoring:
Larval sampling should commence once the adult moths are noted.
Sample at least three locations, a minimum of 50 m apart.
At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae.
Count them and compare the average against the values in the economic threshold table below:
Scouting tips:
Some bertha armyworm larvae remain green or pale brown throughout their larval life.
Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms.
Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves.
Larvae eat the outer green layer of the stems and pods exposing the white tissue.
At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.
Keep track of the Provincial Entomologist Updates for the latest in-season pheromone trap monitoring results for 2018.
Albertans can access the online reporting map (screenshot retrieved 19Jun2018 provided below for reference:
Lygus bugs (Lygus spp.) – The model indicated that Lygus populations range between the 1st – 4th instar stages with the average being second instar stage. The greatest development is predicted to occur across southern Manitoba and Saskatchewan (Fig. 1). The model suggests that Saskatoon populations consist of first to third instar stages (Fig. 2).
Figure 1. Lygus development (average instar) based on model simulations, for April 1 – June 18, 2018.
Figure 2. Predicted Lygus phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 18, 2018.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel. Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut. Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net. Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected. Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836). Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Diamondback moth (Plutellidae: Plutella xylostella) – Once the diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Monitoring: Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
Figure 2. Diamondback moth pupa within silken cocoon.
Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant). Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).
Figure 3. Diamondback moth.
Across the prairies, provincial staffs coordinate diamondback pheromone trapping during the growing season. Every spring, the early arrival of diamondback moths (Fig. 3) is monitored through the tracking of high level air masses that originate from the south of North America and arrive across the Canadian prairies. Additionally, pheromone traps are deployed to intercept the initial moths. Cumulative male moth counts occurring over a 6-7 week period of trapping are used to estimate relative risk for the growing season. Vast networks of cooperators across Manitoba, Saskatchewan, Alberta, and the BC Peace work with their provincial entomologists to generate the following in-season results:
● Counts are summarized by Saskatchewan Agriculture (updated June 15, 2018, by J. Tansey):
● Manitoba Agriculture generally reports low DBM counts so far but review the specifics by region within the latest Insect and Disease Update (June 6, 2018).
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring: ● Begin sampling when the crop first enters the bud stage and continue through the flowering. ● Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location. ● Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field. ● Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur. ● An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). ● Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators. ● High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod. There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Reminder – The 2017 cabbage seedpod weevil distribution map was circulated in January and is posted below for reference. Note that areas highlighted orange or red in the map below included fields with comparatively higher densities of the weevil in 2017 so in-field scouting is particularly important in these same areas in 2018.
This week’s Insect of the week is the red turnip beetle (Coleoptera: Chrysomelidae). This beetle is 7-10 millimeters long and has a distinctive red body with black markings on the head and thorax, and three black stripes down its back (elytra). They feed on mustards, canola, cole crops, and cruciferous weeds (except stinkweed).
They overwinter as reddish brown oval eggs in the soil. Adults emerge in the spring to feed for 2-3 weeks before re-entering the soil to escape the summer heat. When they re-emerge, they disperse throughout the host crop, feeding, mating, and laying eggs (300-400/female). Feeding damage can cause delayed harvest or need for re-seeding to replace killed plants. Later in the season they feed on leaves, stems, and pods. Attached pods are prone to premature shelling.
For more information about the red turnip beetle, have a look at our Insect of the Week page!
Red turnip beetle adult and damage
John Gavloski, Manitoba Agriculture, Food and Rural Development
Bertha armyworm (Lepidoptera: Mamestra configurata) – BAW development continues to be 7-10 days ahead of normal development (Fig. 1).
Figure 1. Percentage of pupal stage heat requirements for emergence of bertha armyworm (as of June 20, 2018).
Near Saskatoon SK, adult emergence is well underway and oviposition is predicted to have begun this week. Based on climate data, oviposition near Saskatoon should begin around the third week of June.
Reminder –Table 1. Projected dates for BAW adult emergence for June 4, 2018 (projected to June 30, 2018).
For those who are now checking a bertha armyworm pheromone trap on a weekly basis, we provide an excellent photo kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions. Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths so check carefully and thanks for your help!
Lygus bugs (Lygus spp.) – Lygus development is well underway. Adults have moved in to the fields and oviposition should be almost complete. The Lygus model suggests that populations near Brandon MB should consist of first to third instar stages (Fig. 1).
Figure 1. Predicted Lygus phenology at Brandon MB.
Values are based on model simulations, for April 1 – June 11, 2018.
On average, prairie populations are predicted to be in the first or second instar stages with development being greatest across the southern prairies (Fig. 2).
Figure 2. Predicted average developmental Lygus stage.
Values are based on model simulations, for April 1 – June 11, 2018.
Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel. Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut. Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net. Repeat the sampling in another 14 locations. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.
Sequential sampling for lygus bugs at late flowering stage in canola.
The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected. Table 1. Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).
1 Canola crop stage estimated using Harper and Berkenkamp 1975). 2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836). Table 2. Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).
3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).
Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring: ● Begin sampling when the crop first enters the bud stage and continue through the flowering. ● Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location. ● Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field. ● Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur. ● An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). ● Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators. ● High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod. There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Bertha armyworm (Lepidoptera: Mamestra configurata) – The BAW model is predicting that pupae are developing rapidly in the soil and that development is well ahead of average (Fig. 1). Development is expected to be 5 – 6 days faster than average.
Though cooler temperatures have slowed BAW development, moths are predicted to emerge 10 days ahead of average (Table 1). Pupal development is approximately 82% (Fig. 1). Model output predicts that emergence may begin as early as June 9th.
Table 1. Projected dates for BAW adult emergence for June 4, 2018 (projected to June 30, 2018).
Figure 1. Predicted bertha armyworm pupal development (as of June 3, 2018).
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring: ● Begin sampling when the crop first enters the bud stage and continue through the flowering. ● Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location. ● Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field. ● Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur. ● An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). ● Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators. ● High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod. There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
Flea Beetles (Chrysomelidae: Phyllotreta species) – The Insect of the Week features flea beetles!
Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding. Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Canola Watch circulated this article but also use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) – take it scouting!
Figure 1. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).
Figure 2. Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).
Refer to the flea beetle page from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.
Bertha armyworm (Lepidoptera: Mamestra configurata) – The BAW model is predicting that pupae are developing rapidly in the soil and that development is well ahead of average (Fig. 1). Development is expected to be 5 – 6 days faster than average.
Figure 1. Predicted bertha armyworm pupal development (as of May 30, 2018).
Pupal development is approximately 72% (long term average is 47%). Model output predicts that emergence may begin as early as June 6, 2018 (Table 1).
Table 1. Projected dates for bertha armyworm adult emergence as of May 28, 2018 and projecting to June 30, 2018.
Reminder – Review the 2017 bertha armyworm distribution map for the Canadian prairies which reports cumulative pheromone trap counts intercepting male moths during the 2017 growing season.
Cabbage seedpod weevil (Ceutorhynchus obstrictus) – There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo). Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.
Monitoring: ● Begin sampling when the crop first enters the bud stage and continue through the flowering. ● Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location. ● Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field. ● Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur. ● An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). ● Consider making insecticide applications late in the day to reduce the impact on pollinators. Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators. ● High numbers of adults in the fall may indicate the potential for economic infestations the following spring.
Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss. Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo). Eggs are oval and an opaque white, each measuring ~1mm long. Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod. There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo). The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell. Approximately 10 days later, the new adult emerges to feed on maturing canola pods. Later in the season these new adults migrate to overwintering sites beyond the field.
This week’s Insect of the Week is the Flea Beetle (Phyllotreta species). This group of beetles is typically oval and 2-3 mm long. In canola, the most common flea beetles are either bluish black (crucifer flea beetle or Phyllotreta cruciferae) or black with two wavy yellow lines running down the length of its back (striped flea beetle or Phyllotreta striolata). They overwinter as adults under plant material along field margins and females lay eggs in the soil near the host plants. Striped and crucifer flea beetles feed on canola, mustard and related cruciferous plants and weeds. Their damage results in a shot-hole appearance in cotyledon leaves. They also feed on stems under windy or damp conditions, causing wilting or breakage. Remember, the Action Threshold for flea beetles on canola is when 25% of cotyledon leaf area is consumed.
For more information on flea beetles, refer to the Insect of the Week page!
