Category: Week 10

2023 WEEK 10 (Released July 12, 2023)

Insect scouting season continues! Development of many pest insects (and of their host crops) is ahead of schedule this year, thanks to warmer than average weather in May and June.

Adult grasshoppers are becoming more common across the prairies now. Although grasshoppers are more widespread this year than in the past few years, the stage of grasshopper development and grasshopper population densities can vary between even relatively close locations. Scouting individual fields is important to best estimate crop risk.

The first adult wheat midge of 2023 were reported in Saskatchewan in late June. Adult flight may have peaked in some areas, but scouting remains important in wetter areas of the prairies.

Diamondback moth could be entering into the third non-migrant generation in some areas this week (if present). Check back next week for a more in-depth update on diamondback moth development but keep in mind that diamondback moth develop quickly in warm weather which could lead to rapidly increasing populations over the summer. Use the links in the Provincial Insect Updates post to learn about diamondback moth and bertha armyworm risk in your region and scout accordingly.

There is now a monitoring protocol for canola flower midge! As canola flowering finishes, it can be easy to see the galled flowers that result from infestation by canola flower midge, so the time to scout could be now or coming soon. A three-year survey completed in 2019 found that canola flower midge is quite widely distributed across the prairies, but in relatively low densities and probably doesn’t cause economic yield losses. If you scout for canola flower midge this year and are willing to share your results please send them to meghan.vankosky@agr.gc.ca. If we get enough information, we will map the results!

This is a busy time for our field research programs across western Canada and with upcoming field days, we are even busier. A list of events can be found on the Prairie Pest Monitoring Network homepage and in this weekly update. Read about the AAFC display planned for Ag in Motion in the latest edition of Science News from the Prairies – find a link to the newsletter in the Prairie Research post where we also feature a new research project focused on the lesser clover leaf weevil.

This week, the Insect of the Week featured Macroglenes penetrans, a parasitoid that attacks wheat midge. Diamondback moth is on our schedule for next week!

Remember, insect Monitoring Protocols containing information about in-field scouting as well as information about insect pest biology and identification.

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Questions or problems accessing the contents of this Weekly Update? Please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) to get connected to our information. Past Weekly Updates, full of information and helpful links, can be accessed on our Weekly Update page.

Weather Synopsis

During the week of July 3-9, 2023, the warmest weekly average temperatures occurred across most of the Peace River region, southern Alberta and southwestern Saskatchewan (Fig. 1). The coolest temperatures during the same week occurred across the Parkland region of Manitoba and Saskatchewan. The prairie average daily temperature was similar to that expected based on climate normals. In fact, a number of locations reported temperatures that were cooler than normal; in northeastern Saskatchewan, for example, some locations had weekly average temperatures that were 2°C cooler than normal.

Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of July 3-9, 2023. 

Average temperatures over the past 30 days (June 10 – July 9, 2023) have been almost 2°C above normal; many locations in the Peace River region have reported 30 day average temperatures that were 3°C warmer than average. The warmest 30-day average temperatures were reported across most of the southern prairies, particularly southern Manitoba (Fig. 2).

Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 10 to July 9, 2023. 

Precipitation for the period of July 3-10, 2023 was minimal across most of the prairies (Fig. 3).

Figure 3. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 3-9, 2023. 

Cumulative rainfall for the past 30 days has been greatest in the Edmonton region (Fig. 4). The lowest rainfall amounts continue to be those reported across most of Saskatchewan and southern Alberta. Conditions continue to be dry across most of the prairies.

Figure 4. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 10 to July 9, 2023. 

Prairie rain amounts for June 10-July 9 have been 72% of normal on average across the prairies. Most of Saskatchewan has had less than 40% of normal rainfall (Fig. 5). Southern Alberta and most of Manitoba have had rainfall amounts that are less 60% of normal (Fig. 5). 

Figure 5. The percent of normal precipitation (based on cumulative rainfall, in mm) over the last 30 days (June 10 to July 9, 2023) observed across the Canadian prairies.

Predicted Grasshopper Development

Model simulations were used to estimate the status of grasshopper development as of July 9, 2023. As a result of warmer than normal temperatures, grasshopper development continues to be well ahead of average. As of July 9. 2023, the average predicted instar for grasshopper populations across the prairies is 4.9, which is significantly greater than the long term average of 3.1 for this time of year. Simulations indicate that 70% of the prairie population should be in the fifth instar or adult stage (Fig. 1).

Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 9, 2023. 

In a ‘normal’ year, we would expect that 57% of the grasshopper population would be in the third or fourth instar in early July (Fig. 2).

Figure 2. In an average year (based on 30-year average weather or climate normals), we expect that about 57% of the grasshopper population would be in the third or fourth instar in early July, as pictured here on the map. In contrast, in 2023, warm weather has significantly sped up the rate of grasshopper development (Fig. 1). 

Reports from across the prairies indicate that adult grasshoppers are now occurring. This is much earlier than normal, but agrees with our model simulations, which predict that adult grasshoppers are now occurring across most of the prairies (Fig. 3). Based on earlier than normal appearance of adults, high densities and drought conditions, grasshopper risk may be significant for large areas of Alberta and Saskatchewan as well as southern Manitoba. 

Figure 3. The proportion (%) of the migratory grasshopper (Melanoplus sanguinipes) population expected to be in the adult stage across the Canadian prairies as of July 9, 2023. 

Models and geospatial maps are tools to help time in-field scouting on a regional scale but grasshopper development and population densities can vary even between relatively close locations. Thus, grasshopper populations are best assessed through scouting. Monitor roadsides and field margins to assess the developmental stage and densities of local grasshopper populations.  

Information about grasshoppers and grasshopper monitoring is available from the Prairie Pest Monitoring Network, Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, and Manitoba Agriculture and in the Field Crop and Forage Pests guide.

Predicted Wheat Midge Development

Wheat midge (Sitodiplosis mosellana) emergence is limited when soil moisture is lacking. Dry conditions in southcentral Manitoba as well as central and southern regions of Alberta have likely resulted in reduced emergence of larvae from the soil. The wheat midge development model indicates that peak emergence of adults is now occurring. Oviposition is predicted to have begun across most of the prairies and eggs should be the most abundant lifestage (Fig. 1).

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) population that is predicted to be in the egg stage in western Canada, as of July 9, 2023. Note that wheat midge may not be active in all parts of the prairies, for example in regions where populations were absent last year or in regions where it did not rain in May and June.

In fields across Saskatchewan and western Manitoba, if wheat midge are present, model simulations indicate that egg development is progressing and larvae should be present (Fig. 2).

Figure 2. Percent of the wheat midge (Sitodiplosis mosellana) population that is predicted to be in the larval stage (in wheat heads) in western Canada, as of July 9, 2023. 

The wheat midge model, run for Regina, Saskatchewan indicates that adult emergence has peaked (Fig. 3) in that area. Oviposition should peak later this week. Larval populations (in wheat heads) should reach peak populations later next week.  

Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) near Regina, Saskatchewan as of July 9, 2023. 

Based on the occurrence of wheat midge adults, field monitoring should begin now, if it has not started already. In order to assess wheat midge populations and to take the appropriate action for management, it is recommended that fields should be monitored when wheat is between heading and flowering. Field inspection should be carried out after 8:30 p.m. when the female midge are most active. Females are more active when the temperature is above 15°C and wind speed is less than 10 km/h. Wheat midge populations can be estimated by counting the number of adults present on four or five wheat heads. 

For more information about scouting and economic thresholds, check out the wheat midge monitoring protocol and the Insect of the Week for Week 8, that featured wheat midge. More information is available from Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, and Field Crop and Forage Pests and their Natural Enemies in Western Canada available for free download from our Field Guides page.

Canola Flower Midge Scouting

Scouting for canola flower midge tends to be easiest as the flowering stage of canola ends and pod development begins. Female canola flower midge lay eggs on developing canola buds and larvae develop inside the buds, resulting in galled flowers that do not open or produce pods.

A canola raceme with galled flowers containing canola flower midge larvae; these galled flowers will not produce pods. Picture credit: Boyd Mori, University of Alberta.

From 2017-2019, entomologists and volunteers across the prairies conducted a survey to determine the range of canola flower midge (Fig. 1). There has not been a formal survey conducted since 2019.

Figure 1. Density of canola flower midge, based on the number of galled flowers per raceme across the prairie region observed during a survey conducted in 2017, 2018, and 2019. Map credit: Shane Hladun; map modified from Vankosky et al. (2022).

Although canola flower midge does not appear to occur at densities that cause economic damage, scouting for canola flower midge will help to monitor population growth at the local scale to avoid surprises in the future. The monitoring protocol used from 2017-2019 is now available online so that everyone can scout for canola flower midge.

*If you cannot follow the link to the protocol, please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca).

Upcoming Events

Several field days are coming up! Entomologists, weed scientists, and plant pathologists from across western Canada will be attending various events over the next few weeks. Please look for us – we love to talk about insects, weeds, and plant diseases! A partial list of upcoming events (in no particular order and with no endorsement intended) includes:

Ag in Motion, July 18-20, 2023 at Langham, Saskatchewan.

2023 Lacombe Field Day, July 26, 2023 from 8:00 am to 4:30 pm MDT. Use this link to register.

Saskatchewan Crop Diagnostic School, July 25 or July 26, 2023 at Indian Head, Saskatchewan. It looks like registration for July 25 is maxed out, but spots are still available on July 26.

North Peace Applied Research Association Tour on July 27, 2023 in the Peace River region.

Prairie Research

Science News from the Prairies

A new issue of the newsletter, Science News from the Prairies is now available! This issue highlights the Agriculture and Agri-Food Canada information booth that can be found at Ag in Motion (July 18-20, 2023), new publications arising from prairie research, and upcoming events.

Developing Economic Thresholds for Lesser Clover Leaf Weevil

*This text was prepared by Jeremy Irvine and Sean Prager from the University of Saskatchewan.

Red clover (Trifolium pratense) is a short-lived perennial crop grown for seed production. Red clover seed is an important commodity in the Canadian Prairies, providing upwards of $2 million annually to the Saskatchewan economy. The production of red clover seed can be affected by the lesser clover leaf weevil (Hypera nigrirostris; LCLW). Yield losses of up to 50% have been recorded with high infestations of the LCLW. The weevil larvae feed on the developing shoots, flower heads, and seeds of red clover plants. Larvae cause the worst damage but secondary feeding damage can occur once LCLW larvae become adults.

Lesser clover leaf weevil damage, resulting when larvae exit the stem of the host plant. Picture credit: Jeremy Irvine, University of Saskatchewan.

Lesser clover leaf weevils are traditionally controlled using insecticides, but these can have negative impacts on  non-target insect species, notably bees. Managed bee species are used by red clover seed growers to ensure fields receive adequate pollination, high seed set, and subsequent yield.

There are currently no established economic thresholds for control of LCLW and insecticides can be applied when they are not needed, which increases the cost of clover production, negatively affects pollinators, and could contribute to the development of insecticide resistance in the LCLW population. The threat of insecticide resistance is significant because there is only one registered active ingredient for LCLW.  

A field trial near Carrot River, Saskatchewan is set up in second-year red clover to study the lesser clover leaf weevil. Picture by Jeremy Irvine, University of Saskatchewan.

The primary purpose of this research, which began in May 2023, is to develop an economic thresholds for LCLW in red clover crops. The project will also study the development of LCLW in varying weather conditions so that seasonal development can be incorporated into the economic thresholds. Finally, the project will generate a sequential sampling plan, meant to assist with the decision-making process to optimize management of LCLW. To conduct this research, we will work with farmers to conduct on-farm field trials where LCLW population densities will be manipulated and red clover yield will be quantified to determine the relationship between weevil density, injury level, and yield loss.

The overall goal of our project is to develop new tools that can be used to manage LCLW and protect red clover seed yields. Financial support for this study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Government of Saskatchewan Agriculture Development Fund (ADF) and the Saskatchewan Forage Seed Development Commission (SFSDC).

Provincial Insect Updates

Visit the Alberta Insect Pest Monitoring Network and Crop Insects pages for information about insects and monitoring in Alberta, including links for live maps from the 2023 monitoring season for diamondback moth, bertha armyworm, cutworms, and cabbage seedpod weevil.

Saskatchewan Crop Production News issues are now online! Use this link to read Issue #2 and watch for future issues. Issue #2 for 2023 includes information plant diseases and plant staging for pesticide applications. There are links on the Crop Production News page so that interested readers can subscribe to the newsletter.

Weekly Manitoba Crop Pest Updates for 2023 are available online with timely updates about insect pests, weeds, and plant pathogens. Watch their website for new Crop Pest Updates (usually published on Wednesdays this year).

MACROGLENES PENETRANS IS THE NEMESIS OF WHEAT MIDGE

Macroglenes penetrans is a beneficial parasitoid wasp from the family Pteromalidae. It is an important natural enemy of wheat midge. This small, black wasp can be seen emerging in large numbers from wheat stubble shortly after wheat midge adults are first sighted. This means that often they are emerging into canola fields and then have to disperse to find wheat fields where their hosts are active. Macroglenes penetrans is a parasitoid that lives inside the wheat midge larva and overwinters within the wheat midge larval cocoon. In the spring, the parasitoid larva develops to emerge from the wheat midge cocoon buried in the soil and then the adult parasitoid seeks out wheat midge eggs. 

A very small adult Macroglenes penetrans on a wheat head. Picture credit: Shelby Dufton, AAFC Beaverlodge Research Farm.

Macroglenes penetrans is an important part of wheat midge management – parasitism rates can reach upwards of 70% of the wheat midge population! The numbers of this parasitoid overwintering inside wheat midge cocoons are counted during the fall soil core survey, so that the survey map only includes counts of non-parasitized wheat midge.  

Biological and monitoring information related to Macroglenes penetrans and the wheat midge in field crops can be found in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien). 

Released July 15, 2022

This week includes…..

• Weather synopsis
• Predicted wheat midge development
• Predicted grasshopper development
• Predicted diamondback development
• Provincial entomologist updates
• Links to crop reports
• Previous posts
….and Monday’s Insect of the Week for Week 10 – it’s cereal thrips (various species) and European skipper (Thymelicus lineola)!

Wishing everyone good SCOUTING weather!

To receive free Weekly Updates automatically, please subscribe to the website!

Questions or problems accessing the contents of this Weekly Update?  Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.

Weather synopsis

TEMPERATURE: Though recent temperatures have been warmer than normal, the 2022 growing season across the prairies continues to be cooler than average. This past week (July 4-10, 2022) the average daily temperature for the prairie region was 2.5 °C warmer than last week. The warmest temperatures were observed across the southern prairies, particularly southeastern Saskatchewan and Manitoba (Fig. 1). The prairie-wide average 30-day temperature (June 11 – July 10, 2022) was 1 °C warmer than the long-term average value. Average temperatures have been warmest across the southern prairies, particularly in Saskatchewan and Manitoba (Fig. 2).

Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 4-10, 2022.
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 11-July 10, 2022.

The average growing season (April 1-July 10, 2022) temperature for the prairies has been 0.5 °C cooler than climate normal values. The growing season has been warmest across a region than extends from Lethbridge to Regina and Saskatoon as well as southern Manitoba (Fig. 3).

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 10, 2022.

PRECIPITATION: Weekly (July 4-10, 2022) rainfall varied across the prairies. The highest rainfall amounts were reported across central Alberta and southern Saskatchewan (Fig. 4). The Peace River region and central Saskatchewan reported rainfall amounts that were generally less than 10 mm. The 30-day (June 11 – July 10, 2022) rainfall accumulation amounts have been well above average for Alberta, near normal to above normal across Manitoba, and well below normal for Saskatchewan (Fig. 5).

Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 4-10, 2022.
Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 11-July 10, 2022).

Growing season rainfall for April 1 – July 10, 2022, continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been lower for central and western regions of Saskatchewan and Alberta (Fig. 6).

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 10, 2022.

Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-July 11, 2022) can be viewed by clicking the hyperlinks. Over the past 7 days (July 5-11, 2022), the lowest temperatures recorded across the Canadian prairies ranged from < -2 to >14 °C while the highest temperatures observed ranged from <23 to >33 °C. Review the days at or above 25 °C across the prairies and also the days at or above 30 °C. Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Current Conditions Maps for the growing season. Historical weather data can be accessed at the AAFC Drought Watch Historical website, Environment Canada’s Historical Data website, or your provincial weather network. The AAFC Canadian Drought Monitor also provides geospatial maps updated monthly.

Predicted wheat midge development

Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Where wheat midge cocoons are present in soil, the 2022 growing season’s rainfall during May and June should be sufficient to terminate diapause and induce the larvae to move to the soil surface.

The following maps represent predicted regional estimates of wheat midge development. Remember – the rate of development and timing of adult midge emergence varies at the field level and can only be verified through in-field scouting. Midge flight coinciding with the beginning of anthesis is a crucial point when in-field counts of adults on plants are carefully compared to the economic thresholds!

As of July 10, 2022 and where wheat midge is present, model simulations predict that pupae, adults, and eggs are present in wheat fields across the prairies. Differences in wheat midge development are attributed to rainfall differences across the prairies. Due to drier conditions in May and June, wheat midge development was delayed across most of Alberta. Alberta populations should be predominantly in the pupal stage (Fig. 1).

Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the pupal stage, across western Canada, as of July 10, 2022.

The appearance of adults is predicted to increase across all three provinces (Fig. 2). Optimal rain in May and June across Saskatchewan and Manitoba has resulted in development rates that are greater than those predicted for Alberta. The simulation indicates that oviposition has begun across eastern Saskatchewan, Manitoba, the Peace River region and north-western Alberta (Fig. 3). Larvae may be in wheat heads in a region south of Winnipeg.

Figure. 2. Percent of wheat midge population (Sitodiplosis mosellana) that is in the adult stage across western Canada, as of July 10, 2022.
Figure 3. Percent of wheat midge population (Sitodiplosis mosellana) that is in the egg stage, across western Canada, as of July 10, 2022.

Adults may be occurring when wheat is most susceptible. Adults and eggs (top panel) are predicted to occur when wheat is heading (bottom panel) for fields near Regina, Saskatchewan (Fig. 3). Phenology simulations suggest that wheat may be susceptible for the next two weeks.

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of July 10, 2022.

In-Field Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 5). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 5. Wheat midge (Sitodiplosis mosellana) laying their eggs on a wheat head. Photo: AAFC-Beav-S. Dufton and A. Jorgensen.

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 6), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 6. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  Photo: AAFC-Beav-S. Dufton.

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

Additional information can be accessed by reviewing the Wheat midge pages extracted from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.

Predicted grasshopper development

The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale but local development can vary and is only accurately assessed through in-field scouting.

SCOUT NOW – Some areas of the Canadian prairies are presently experiencing high densities of nymphs and economically important species are present. Review lifecycle and damage information for this pest to support in-field scouting.

Warm, dry conditions across southern and central regions of the prairies have advanced grasshopper development. Model simulations were used to estimate grasshopper development as of July 10, 2022. Based on estimates of average nymphal development, populations are predicted to consist of primarily 4th and 5th instar stages across all three prairie provinces (Fig. 1). Across most of the prairies, grasshopper development is predicted to be similar to average values; development is delayed across southern Manitoba (Fig. 2).

Figure 1. Predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 10, 2022.
Figure 2. Long-term average predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as the average instar, across the Canadian prairies as of July 10, based on climate normal data.

Grasshopper Scouting Tips:
● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species to aid in-field scouting from egg hatch and onwards.
● Access the PPMN’s Grasshopper Monitoring Protocol as a guide to help implement in-field monitoring.
● Review grasshopper lifecycle, damage and scouting and economic thresholds to support sound management decisions enabling the preservation of beneficial arthropods and mitigation of economic losses.

Biological and monitoring information (including tips for scouting and economic thresholds) related to grasshoppers in field crops is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. Review the historical grasshopper maps based on late-summer in-field counts of adults performed across the prairies.

Predicted diamondback moth development

Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.

Model simulations to July 10, 2022, indicate the second generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the Canadian prairies (Fig. 1). DBM development is predicted to be similar to long-term average development for this time of the growing season (Fig. 2).

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 10, 2022.
Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 10, based on climate normal data.

Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative DBM data are available for Manitoba, Saskatchewan and Alberta. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.

In-Field Monitoring: Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto 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.

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).

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Figure 3. Diamondback moth pupa within silken cocoon.
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Figure 4. Diamondback moth.

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the diamondback moth pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.

Diamondback moth was the Insect of the Week for Wk10 in 2021!

Provincial insect pest report links

Provincial entomologists provide insect pest updates throughout the growing season so link to their information:

MANITOBA’S Crop Pest Updates for 2022 are up and running! Access a PDF copy of the July 13, 2022 issue here. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more!
• Pea aphids in MB were emphasized in the July 13 issue.
• Bertha armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 11, 2022) of cumulative weekly counts.
• Armyworm pheromone trap monitoring is underway in MB – Review this summary (as of June 28, 2022) of counts compiled from Manitoba, Eastern Canada and several northeast states of the United States.

SASKATCHEWAN’S Crop Production News for 2022 is up and running! Access the online Issue #4 (July 14, 2022) here and find updates linking to information for Wheat stem sawfly. Bookmark their insect pest homepage to access important information! Crops Blog Posts are updated through the growing season and note this link for July’s Crop Diagnostic School.

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
• Wheat midge pheromone monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
• Cabbage seedpod weevil monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
• Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.

Crop report links

Click the provincial name below to link to online crop reports produced by:
• Manitoba Agriculture and Resource Development (or access a PDF copy of the July 12, 2022 report).
• Saskatchewan Agriculture (or access a PDF copy of the July 5-11, 2022 report).
• Alberta Agriculture, Forestry, and Rural Economic Development (or access a PDF copy of the June 27, 2022 report).

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 11, 2022 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 12, 2022 edition).

Previous posts

As the growing season progresses, the various Weekly Update topics move on and off the priority list for in-field scouting but they should be kept at hand to support season-long monitoring. Click to review these earlier 2022 Posts (organized alphabetically):
• 2021 Risk and forecast maps
• Alfalfa weevil – predicted development (Wk06)
• Bertha armyworm – predicted development (Wk07)
• Cereal leaf beetle – predicted development (Wk06)
• Crop protection guides (Wk02)
• Cutworms (Wk02)
• European corn borer – Canadian standardized assessment 2.0 (Wk02)
• Field heroes (Wk08)
• Field guides – New webpage to access (Wk02)
• Flea beetles (Wk01; IOTW)
• iNaturalist.ca (Wk02)
• Invasive insect species – Early detection (Wk02)
• Scouting charts – canola and flax (Wk03)
• Ticks and Lyme disease (Wk02)
• Wind trajectory reports released in 2

Thrips in small grains cereal crops

Thrips (used for both singular and plural) are members of the Order Thysanoptera. Even more confusing, there is also a genus of thrips named Thrips. That is, all Thrips are thrips but not all thrips are Thrips!

Thrips are characterized by small size (the largest species is only 2 mm as adults; the smallest is 0.6 mm), long slender bodies, and fringed wings (winged and wingless adults exist in some species). Males are smaller than females.

Figure 1: Adult thrips on barley leaf showing off fringed wings neatly folded over its abdomen. Photo: Sheila Elder, Saskatchewan, Canada

Adult thrips are generally relatively weak flyers and employ a‘clap and fling’ technique. The animal claps the leading edges of its wings together at the end of the upstroke then rotates the wings around the trailing edges, flinging them apart. Many small insects use this technique to promote air circulation and generate lift quickly. Pigeons also use this technique for their noisy flight initiations. For small insects, the viscosity of the air has a much greater effect than on larger animals. Fringed wings reduce drag associated with this effect.  

There are about 6,000 species of thrips worldwide with 147 described species in two suborders in Canada, including 28 non-natives. Recent molecular work indicates that there may be as many as 255 additional as-yet-undescribed species in Canada. The most common and broadly distributed family is the Thripidae, followed by the Phlaeothripidae and Aeolothripidae. Other families are far less represented.

Although some species are important for pollination and a few are predators of other small insects, some are pests in crops. They have unique, asymmetrical mouthparts characterized by a greatly reduced right mandible. Their feeding is described as ‘rasping-sucking’: they scrape the surface of plant tissue and ingest fluid flowing from the wound. When feeding on actively growing plant tissue, growth reductions and distorted growth may be observed and yield loss can occur. When they feed on more mature tissue, silver leaf scars can occur that reduce the quality and marketability of some crops. Thrips are also important vectors of topsoviruses.

One suborder of thrips lays very small eggs (0.08 mm to 0.2 mm) singly in slits in plant tissue; the other lays eggs on plant surfaces. Eggs hatch into nymphs: juveniles resemble adults but are not sexually mature and have no wings. There are two juvenile feeding stages, followed by two non-feeding stages: pre-pupa and pupa.   

The barley thrips, Limothrips denticornis, was first reported in North America in 1923 in New York. In its native Europe and Asia, it can be found on a wide variety of grass species but is a minor pest and only on rye. In North America, it is generally more important on barley, though it can be found on winter wheat, durum, winter rye, corn, and triticale. Adults are small (1.1 mm to 1.8 mm), elongate, and dark brown to black. These thrips lay eggs on upper leaf sheaths and each female can produce 100 eggs. Juveniles are smaller and lighter coloured. Barley thrips overwinter as adults and move to winter grasses in the spring. They are somewhat stronger flyers than many thrips species, but are still limited by their size. In Northern Europe, cereal thrips, including L. denticornis, have been reported to appearin large numbers ahead of thunderstorms. This may be associated with the warm conditions that precede these events, but it has also been suggested that they are sensitive to the electrical fields associated with storms.    

Another cereal thrips, Limothrips cerealium, has also been reported in Canadian small grains cereals and was reported in 1928 to be responsible for 10 per cent losses in oats in Canada.

Thrips feeding on cereals can result in tissues appearing bleached. When numbers are high and feeding is intense, kernels can be shriveled. Severe flag leaf feeding can result in kernels filling improperly and reduced kernel weight.

Figure 2: Thrips nestled at the base of leaf. Photo: Sheila Elder, Saskatchewan, Canada

Scouting for barley thrips should be done from first sign of flag leaf until the head is completely emerged from the boot. Barley thrips can be found on stems but are more commonly under the top two leaf sheaths. Because thrips are relatively weak flyers, there may be greater concentrations in protected field edges. Greatest damage has been reported in dryland cropping areas after prolonged drought.

Economic thresholds:

Threshold (thrips/stem) = (Cost of control per acre / expected $ value per bushel) / 0.4

.Sample at least 50 stems from different parts of the field. One adult thrips per stem can cause a loss of 0.4 bushels per acre. This usually translates to an action threshold for barley and oats of 7 – 8 thrips/stem prior to head emergence but greater precision can be achieved by using the formula. The action threshold is the number of insects detected that can cause enough damage to justify the expense and effort of applying control. Numbers lower than this do not warrant control. Only apply control prior to the completion of heading.

Thresholds for cereal thrips have been determined for barley and oats but effects on other cereals crops in North America are less well understood. Work in Europe indicated comparable damage per thrips in rye, triticale, and winter barley. Recent reports of barley thrips in durum also suggest a risk of damaging effects, but these are not as well understood. A report from Germany indicated that, despite some relatively high thrips numbers, there was no correlation between barley thrips and damage. However, there is also evidence from Europe of the importance of long crop rotation to thrips damage control in wheat.

European Skipper: Invasive to Established in Western Canada

Even damaging insects can be beautiful! In fact, showy invasive species often are detected earlier compared to smaller, less colourful, or more cryptic or camouflaged species. The European skipper (Hesperiidae: Thymelicus lineola) is a good example of a bright orange butterfly large enough to easily spot on the wing that is diurnal (Fig. 1, 6). Unfortunately, the predominantly green larvae are defoliators capable of causing economic levels of damage in timothy but they also feed on a number of other grasses and winter wheat.

Figure 1. European skipper (Thymelicus lineola) adults on timothy seed heads. Photo: S. Dufton, AAFC-Beaverlodge.

There is one generation per year of European skipper but butterfly oviposition or egg laying largely dictates where damage occurs the following summer.  Early in July, butterflies feed on nectar, mate, and lay eggs. Females lay vertical rows or “strings” of groups of ~30 eggs on the inside of grass leaf sheaths, seed heads or on the stem of a host plant. By late July, larvae develop within the eggs yet they remain safely enclosed to overwinter inside the egg shell. Early in May, the overwintered larvae emerge from the shell, crawling up growing grass blades to feed. Five larval instar stages cause damage by defoliation of the upper leaves of timothy. Adult wingspans range from 19-26 mm but they have bright brassy orange wings with narrow black borders and hindwing undersides that are pale orange and greyish. The typical flight season extends from early June to mid-July but will vary regionally with southern parts of the Canadian prairies starting earlier than more northern regions.

Larvae are leaf-tyers that spin and attach silk ties across the outer edges of leaves to pull them together (Figs. 2-5). The silk ties hold the leaf in a tight furl enclosing the larva within a leafy tube then it moves up and down the tube to feed. The tying behavior and camouflaged green body (marked longitudinally with two white lines) make larvae hard to locate when scouting.  Even larger larvae with their brown head capsules are surprisingly difficult to locate because the larva will lie lengthwise, along the base of the leaf fold yet remain very still until touched. When high densities of European skipper larvae are present, leaf tying goes out the window and larvae feed in more exposed areas, often amidst rapidly disappearing foliage.

Figure 2. Early instar larva feeding along edge of timothy leaf. Photo: A. Jorgensen, AAFC-Beaverlodge.
Figure 3. Larva resting in fold of timothy leaf formed by silken tie. Photo: K. Pivnick, AAFC-Saskatoon.
Figure 4. Larval feeding damage and silken ties on timothy leaf. Photo: K. Pivnick, AAFC-Saskatoon.

European skipper (Thymelicus lineola) was introduced to North America decades ago and has moved west and north in its distribution across western Canada even though its area of origin is recognized as Eurasia and northwestern Africa. The initial report of European skipper in Canada is from 1910 and cites it being imported on contaminated timothy seed near London, Ontario.  Eggs can be transferred in both hay and seed as seed cleaning will not remove all eggs.

Distribution records for T. lineola can be reviewed on the Butterflies of North America website. In western Canada, T. lineola established in parts of Saskatchewan by 2006. In 2008, butterflies were collected near Valleyview, Alberta (Otani, pers.comm.), and in 2015 larvae were observed feeding in the flag leaves of winter wheat near Mayerthorpe, Alberta (2015 Meers, pers. comm.).  Specimens confirmed as T. lineola were collected in 2016 near Valleyview, Donnelly, and High Prairie, Alberta (2017 Otani and Schmidt, pers. comm.) with additional specimens confirmed from Baldonnel and Clayhurst, British Columbia in 2021 (2021 Otani and Schmidt, pers. comm.).

Cultural control strategies for European skipper include separating timothy from nectar sources to avoid attracting adults which will mate then oviposit in the same field.  Another strategy is the removal of cut grass or bales.  In terms of chemical control, an action threshold of six or more larvae per 30 cm x 30 cm area is recommended to mitigate losses but emphasis should be placed on scouting and managing early instar larvae. If the need arises, chemical control in timothy involves using a higher water volume (e.g., 300 L H2O/ha) to adequately cover the thicker canopy.

Figure 5. In situ camouflaged larvae and feeding damage in timothy. Photo: S. Barkley.

Interesting fact: In Europe, Thymelicus lineola is commonly referred to as the Essex Skipper.

Host plants: timothy (Phleum pretense), cocksfoot (Dactylis glomerata), couch or quack grass (Agrophyron repens), perennial ryegrass (Lolium perenne), meadow fescue (Festuca pratensis), orchardgrass (Dactylis glomerata).

Nectar sources for adults: orange hawkweed, thistles, oxeye daisy, fleabane, white clover, red clover, common milkweed.

Resources:
• Alberta Forage Manual https://open.alberta.ca/publications/077326082x
• Excerpt of European skipper pages from the Alberta Forage Manual: https://drive.google.com/file/d/0B_1NQ60rRZGTRkE4R0dwSllSbWc/view?resourcekey=0-FcL4jcaeBHijt50EtEMxsg
• Information from Butterflies of Canada posted at: http://www.cbif.gc.ca/eng/species-bank/butterflies-of-canada/european-skipper/?id=1370403265612
• Butterflies and moths of North America: http://www.butterfliesandmoths.org/species/Thymelicus-lineola
• Health Canada Pesticide Label online search tool (for desktop): https://pr-rp.hc-sc.gc.ca/ls-re/index-eng.php
• Health Canada Pesticide Label Mobile App: https://www.canada.ca/en/health-canada/services/consumer-product-safety/pesticides-pest-management/registrants-applicants/tools/pesticide-label-search.html
• WCCP Guide to Integrated Control of Insect Pests of Crops: https://www.westernforum.org/WCCP%20Guidelines.html

Figure 6. Adults in copula on timothy. Photo: S. Barkley, Brooks, Alberta, Canada.

Weekly Update

Week 10 and our staff are busy out surveying so this is an abridged report! The incredible heat supported the rapid development of field crop insect pests so scouting is absolutely critical! Be sure to review the entire Previous Posts section for help beyond this shorter report. Also catch the Insect of the Week – it’s diamondback moths!

Stay safe and good scouting to you!

Questions or problems accessing the contents of this Weekly Update?  Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.

Weather synopsis

TEMPERATURE: This past week (June 28 – July 4, 2021) an extreme heatwave affected temperatures across most of western North America. The North American heat dome was associated with exceptionally hot weather and resulted in numerous record temperatures across the Canadian prairies. Compared to climate normal temperature values, observed weekly average temperatures were 7.4 °C warmer than average! The warmest temperatures were observed across southern Alberta and western Saskatchewan. Table 1 provides a comparison between observed and average temperatures for the ten warmest locations across the prairies.

Similar to last week, the warmest temperatures were observed across Alberta (Fig. 1). Across the prairies, the average 30-day (June 5 – July 4, 2021) temperature was almost 3 °C warmer than climate normal values. The warmest temperatures were observed across southern Manitoba and southeastern Alberta (Fig. 2).

Figure 1. 7-day average temperature (°C) observed across the Canadian prairies for the period of June 28 – July 4, 2021.
Figure 2. 30-day average temperature (°C) observed across the Canadian prairies for the period of June 5 – July 4, 2021.

The 2021 growing season (April 1 – July 4, 2021) has been characterized by temperatures that have been 1.5 °C warmer than average. The warmest temperatures have occurred across southeastern Manitoba, west-central Saskatchewan and southern Alberta (Fig. 3).

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 – July 4, 2021.

Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-July 5, 2021) can be viewed by clicking the hyperlinks. Over the past 7 days (July 1-7, 2021), the lowest temperatures recorded across the Canadian prairies ranged from < 0 to >12 °C while the highest temperatures observed ranged from <28 to >39 °C. With the incredible heat experienced so far, check the number of days of >25 °C or >30 °C across the Canadian prairies (April 1-July 7, 2021). Access these maps and more using the AAFC Drought Watch webpage interface.

PRECIPITATION: This past week, minimal rainfall was reported across most of the prairies with most locations reporting weekly amounts of less than 2 mm (Fig. 4). Higher rainfall amounts were reported across central Alberta and northern areas across the Peace River region. Rainfall amounts for the period of June 5 – July 4 (30-day accumulation) have been well below average across most of the prairies. The lowest rainfall amounts have occurred across most of Saskatchewan as well as southern and northern regions of Alberta (Fig. 5).

Figure 4. 7-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 28 – July 4, 2021.
Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 5 – July 4, 2021

The average growing season (April 1 – July 4) precipitation was 90 % of normal with the greatest precipitation occurring across eastern Saskatchewan, including Regina. Below normal rainfall has been reported across western Saskatchewan, southern Alberta and the Peace River region(Fig. 6).

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 – July 4, 2021.

The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Current Conditions Maps for the growing season. Historical weather data can be access at the AAFC Drought Watch Historical website, Environment Canada’s Historical Data website, or your provincial weather network.

Predicted wheat midge development

The recent warm temperatures have resulted in rapid development of wheat midge (Sitodiplosis mosellana) populations. Dry conditions in the Peace River region have contributed to delayed development of larval cocoons with 30-75 % of the population not expected to emerge this growing season. Unlike the larval cocoon stage (located in the soil), development of pupal, adult, egg and larval stages (in wheat heads) is not dependent on moisture. Development of these stages are dependent on temperature.

Where present, wheat midge populations should be entering the adult stage across most of the prairies (Fig. 1). This is a substantial change from last week where less than 10 % of the population was predicted to be in the adult stage. Oviposition is predicted to be occurring across most of the prairies and the initial hatch is now expected for southern Manitoba and southeastern Saskatchewan (Figs. 2 and 3).

Figure 1. Percent of wheat midge (Sitodiplosis mosellana) population that is in the adult stage, across the Canadian prairies as of July 4, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the egg stage, across the Canadian prairies as of July 4, 2021.
Figure 3. Percent of wheat midge (Sitodiplosis mosellana) population that is in the larval stage (in wheat heads), across the Canadian prairies as of July 4, 2021.

The model was projected to July 20 to determine potential development at Regina (Fig. 4), Lacombe (Fig. 5), and Grande Prairie (Fig. 6) over the next two weeks. Output suggests that oviposition will rapidly increase over the next 10 days and wheat crops near all three locations may be susceptible for the next two weeks. Based on the predicted occurrence of adults and eggs, development is most rapid where populations were predicted to be greatest in 2021 (based on 2020 fall survey).

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of July 4, 2021 (projected to July 20, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Lacombe, Alberta as of July 4, 2021 (projected to July 20, 2021).
Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta as of July 4, 2021 (projected to July 20, 2021).

Macroglenes penetrans is a parasitoid of wheat midge that is active in wheat fields when wheat midge adults are present. Model simulations indicate that the parasitoid has begun to appear in wheat crops in fields near Regina (Fig. 7).

Figure 7. Predicted occurrence of wheat midge (Sitodiplosis mosellana) and Macroglenes penetrans adults near Regina, Saskatchewan as of July 4, 2021 (projected to July 20, 2021).

If not already underway, scouting for wheat midge adults should continue this week and especially in regions where higher densities are predicted to occur. It is especially important to be monitoring for adults at dusk in regions expected to be at high risk, based on the 2020 survey which is mapped here.

Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 7). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 7. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 8), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 8. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted grasshopper development

Model simulations were used to estimate grasshopper (Melanoplus sanguinipes) development as of July 4, 2021. Recent warm conditions have resulted in a noticeable increase in grasshopper development since last week. Grasshopper development, based on average instar, should be greatest across southern Manitoba and southeastern Saskatchewan (Fig. 1).

Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as the average instar, across the Canadian prairies as of July 4, 2021.

Across the prairies, more than 15 % of the population should be in the fifth instar (Fig. 2). Development, as of July 4, 2021, is well ahead of long-term average values (Fig. 3).

Figure 2. Percent of grasshopper (Melanoplus sanguinipes) population in the 5th instar across the Canadian prairies as of July 4, 2021.
Figure 3. Long-term average predicted grasshopper (Melanoplus sanguinipes) development, presented as the average instar, across the Canadian prairies as of July 4, based on climate normals data.

Grasshopper Scouting Steps:
● Review grasshopper diversity and scouting information including photos of both nymphs, adults and non-grasshopper species to aid in-field scouting and accurately apply thresholds for grasshoppers.
● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.
● Start at one end in either the field or the roadside and walk toward the other end of the 50 m, making some disturbance with your feet to encourage any grasshoppers to jump.
● Grasshoppers that jump/fly through the field of view within a one-meter width in front of the observer are counted.
● A meter stick can be carried as a visual tool to give perspective for a one-meter width. However, after a few stops, one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance.
● At the endpoint, the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure.
● Compare counts to the following damage levels associated with pest species of grasshoppers:
0-2 per m² – None to very light damage
2-4 per m² – Very light damage
4-8 per m² – Light damage
8-12 per m² – Action threshold in cereals and canola
12-24 per m² – Severe damage
24 per m² – Very severe damage
For lentils at flowering and pod stages, >2 per m² will cause yield loss.
For flax at boll stages, >2 per m² will cause yield loss.
● More practically, the following thresholds are offered but, in the event of additional crop stress (e.g., drought), the use of “may be required” versus “control usually required” requires careful consideration:

Biological and monitoring information (including tips for scouting and economic thresholds) related to grasshoppers in field crops is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (accessible in either English-enhanced or French-enhanced versions).

Predicted diamondback moth development

Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season. Diamondback moth is the Insect of the Week for Wk10!

Model simulations to July 4, 2021, indicate that the second generation of non-migrant adults are currently emerging across the Canadian prairies (Fig. 1). Across the prairies, development, as of July 4, 2021, is well ahead of long-term average values (Fig. 2).

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) that are expected to have occurred across the Canadian prairies as of July 4, 2021.
Figure 2. Long-term average predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 4 (based on climate normals data).

Monitoring: Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto 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.

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).

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Figure 3. Diamondback moth pupa within silken cocoon.
This image has an empty alt attribute; its file name is DBM_adult_AAFC-1.png
Figure 4. Diamondback moth.

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the diamondback moth pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (accessible in either English-enhanced or French-enhanced versions).

Previous posts

As the growing season progresses, the various Weekly Update topics move on and off the priority list for in-field scouting but they should be kept at hand to support season-long monitoring. Click to review these earlier 2021 Posts (organized alphabetically):
• 2020-2021 Risk and forecast maps
• Alfalfa weevil – predicted development (Wk07)
• Aphids in field crops (Wk09)
• Bertha armyworm – predicted development (Wk09)
• Cabbage seedpod weevil monitoring (Wk09)
• Cereal aphid manager APP (Wk07)
• Cereal leaf beetle – predicted development (Wk07)
• Crop protection guides (Wk03)
• Cutworms (Wk02)
• European corn borer – nation-wide monitoring project (Wk07)
• Field heroes (Wk08)
• Flea beetles (Wk02)
• Flea beetles – predicted geographic distribution and abundance (Wk04)
• Grasshopper diversity and scouting photos (Wk08)
• Ladybird beetles (Wk03)
• Lygus bug monitoring (Wk09)
• Monarch migration (Wk09)
• Pea leaf weevil (Wk03)
• Scouting charts – canola and flax (Wk03)
• Slugs and their parasites (Wk04)
• Weather radar mapping interface (Wk06)
• Wind trajectories for monitoring insect movement (Wk02)
• Wind trajectories – weekly reports (Wk09)
• Wireworms (Wk02)

West nile virus risk

The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!

As of July 4, 2021 (Fig. 1), C. tarsalis development is most advanced in Manitoba, southern Alberta, and in small pockets in southern Saskatchewan. The map will change very quickly to orange then red (i.e., areas with sufficient heat accumulation for C. tarsalis to emerge). Given the forecast, areas highlighted yellow in the map below (as of July 4) should start to use DEET this week! IF C. tarsalis is present in an area where WNV is active, it may take as little as 12 days for adults to become fully infective with the current warm weather.

Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 4, 2021).

The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date June 21, 2021; retrieved July 8, 2021). The screenshot below (retrieved 08Jul2021) serves as a reference.

Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retried 08Jul2021).

Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.

Provincial insect pest report links

Provincial entomologists provide insect pest updates throughout the growing season so link to their information:

MANITOBA’S Crop Pest Updates for 2021 are now available – access the July 7, 2021 report here. Be sure to bookmark their Crop Pest Update Index to readily access these reports! Bookmark their insect pest homepage to access fact sheets and more!
• Bertha armyworm pheromone trap monitoring update for MB – Cumulative counts arising from weekly data are available here. The initial counts are categorized as “low risk” so far (i.e., 0-300 moths).
• Diamondback moth pheromone trap monitoring update for MB – Trapping has drawn to a close for 2021. Access the summary here. Only 65 traps intercepted moths and the highest cumulative count was 171 moths near Selkirk. Access the summary (as of June 30, 2021). At this point, in-field scouting for larvae remains important.

SASKATCHEWAN’S Crop Production News are available. Access Issue #2 online which includes information on cabbage seedpod weevil, grasshoppers in Saskatchewan, and wheat midge. Be sure to bookmark their insect pest homepage to access important information!
• Bertha armyworm pheromone trap monitoring update for SK – Cumulative counts arising from weekly data is anticipated to be available here.
• Diamondback moth pheromone trap monitoring update for SK – Monitoring has drawn to a close for 2021. Review the final DBM counts. Extremely low numbers have been intercepted. Province-wide, <65 moths have been intercepted (2021Jun28 Carter, pers. comm.). At this point, in-field scouting for larvae remains important.

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, and insect trap set-up videos and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
• Wheat midge pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available so refer to the Live Map. Some sites in central Alberta are beginning to report “high risk” adult counts so synchrony with anthesis will need to be carefully monitored(08Jul2021).
• Cabbage seedpod weevil sweep-net monitoring update for AB – In-field counts can be entered here to populate the Live Map. Some sites in southern Alberta are reporting densities at or above the economic threshold in canola (08Jul2021).
• Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data have begun so refer to the Live Map. Cumulative counts throughout the province report “low risk” numbers of moths so far (08Jul2021).
• Diamondback moth pheromone trap monitoring update for AB – Trapping has drawn to a close for 2021. Refer to the Live Map which reports extremely low numbers of moths intercepted so far (<50 province-wide as of 01Jul2021). At this point, in-field scouting for larvae remains important.
• Cutworm reporting tool – Refer to the Live Map which now reports seven sites with cutworms (as of 01Jul2021).

Crop report links

Click the provincial name below to link to online crop reports produced by:
• Manitoba Agriculture and Resource Development (subscribe to receive OR access a PDF copy of the July 6 2021 report).
• Saskatchewan Agriculture (or access a PDF copy of the June 29-July 5, 2021 report).
• Alberta Agriculture and Forestry (or access a PDF copy of the June 28, 2021 report).

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 6, 2021 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 7, 2021 edition).

DIAMONDBACK MOTHS: UNWANTED VISITORS TO THE CANADIAN PRAIRIES

Diamondback moth (Alberta Agriculture and Rural Development)

Diamondback moths are a migratory invasive species. Each spring, adult populations migrate northward to the Canadian Prairies on wind currents from infested regions in the southern or western USA. Upon arrival to the Prairies, migrant diamondback moths begin to reproduce, resulting in non-migrant populations that may have three or four generations during the growing season. Host plants include canola, mustard and other cruciferous vegetables and weeds.

Diamondback moths lay their eggs on leaves. Hatchling larvae tunnel into the leaves, later emerging to the surface to feed. Damage begins as shot holes and eventually expands to complete skeletonization, leaving only the leaf veins. Larvae also feed on flowers and strip the surface of developing pods and stems. Damage can lower seed quality and crop yield.

Diamondback moth damage (AAFC)

Adults are active moths measuring 12 millimetres long with an 18-20 millimetre wingspan. When at rest, the forewings form a diamond-shaped pattern along the mid-line. Mature larvae are 8-millimetre-long green caterpillars. Terminal prolegs extend backwards, resembling a fork. When disturbed, caterpillars drop towards the ground on a silken thread to avoid harm.

Diamondback moth larva (Alberta Agriculture and Rural Development)

Biological and monitoring information related to diamondback moths in field crops can be found on our Monitoring page as well as on provincial Agriculture Ministry pages (Manitoba, Saskatchewan andAlberta). For more information, visit the diamondback moth page in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).

Weekly Update

This image has an empty alt attribute; its file name is 2020Jun30_PPMN_Logo_Wide-1024x85.png

Happy Birthday Canada!

Warmer temperatures last week continue to move our growing season forward and there are more insects to prioritize on scouting lists again this week. Bertha armyworm pheromone monitoring numbers are coming in as cooperators work with their provincial networks to help assess risk levels in the form of cumulative moth counts.  We are also poised for wheat midge emergence across the prairies and we dedicate this Weekly Update and remember Dr. John Doane, an entomologist whose research on this pest and many other species contributed significantly to insect pest management on the Canadian prairies.

Access information to support your in-field insect monitoring efforts in the complete Weekly Update either as a series of Posts for Week 10 OR a downloadable PDF.

Questions or problems accessing the contents of this Weekly Update? Please email Meghan.Vankosky@agr.gc.ca or Jennifer.Otani@agr.gc.ca. Past “Weekly Updates” can be accessed on our Weekly Update Blog Page.

Sugar Beet Pests / Feature Entomologist: James Tansey

This week’s Insect of the Week featured crop is the sugar beet, a plant that has been grown in southern Alberta since 1925. Our feature entomologist this week is James Tansey.

Sugar Beet
cc by 2.0 Ulrike Leone

Introduced to the Prairies in the mid-20s, sugar beets are the single 100% Canadian sugar source. A crop that loves heat and water, sugar beets require irrigation to thrive. Alberta produces most of the sugar beet in Canada (only Prairie producer) with the rest produced in Ontario. In 2019, sugar beets were seeded on 11,500 hectares (28,500 acres) in Alberta, producing 520,700 metric tonnes (574,000 US tons). This was a 39% decrease compared to 2018 due to unseasonable cold in September and October.

Several pests target sugar beets. Monitoring and scouting protocols as well as economic thresholds (when available) are found in Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management and the Cutworm Pests of Crops on the Canadian Prairies: Identification and Management Field Guide. Additional monitoring protocols exist to control certain pests.

Sugar Beet Field
cc by 2.0 Gille San Martin
Sugar Beet Pests
  • Army cutworm
  • Beet webworm
  • Blister beetle
  • Clover cutworm
  • European corn borer
  • Pale western cutworm
  • Redbacked cutworm
  • Saltmarsh caterpillar
  • Sugar beet root aphid
Saltmarsh caterpillar moth – AAFC

Entomologist of the Week: James Tansey

Name: Dr. James Tansey
Affiliation: Saskatchewan Ministry of Agriculture
Contact Information: James Tansey PhD
Provincial Specialist, Insect/Pest Management
Production Technology
Crops and Irrigation Branch, Saskatchewan Ministry of Agriculture
3085 Albert Street; Room 125
Regina, Canada S4S 0B1
Business: 306-787-4669
Cell: 306-520-3525

HOW DO YOU CONTRIBUTE IN INSECT MONITORING OR SURVEILLANCE ON THE PRAIRIES?

I help to coordinate and conduct insect surveys in several crops throughout Saskatchewan and coordinate diagnostics with the Crop Protection Laboratory located in Regina.

IN YOUR OPINION, WHAT IS THE MOST INTERESTING FIELD CROP PEST ON THE PRAIRIES?

Predatory midges are very cool. Like flea beetles, there is still so much we do not know about these important insects.  

TELL US ABOUT AN IMPORTANT PROJECT YOU ARE WORKING ON RIGHT NOW.

I am working on a project to establish thresholds for pea aphid in field peas and lentils. This project is in collaboration with AAFC and utilizes the expertise of the Redvers, Outlook and Swift Current Agri-ARM sites.

WHAT TOOLS, PLATFORMS, ETC. DO YOU USE TO COMMUNICATE WITH YOUR STAKEHOLDERS?

I communicate with stakeholders at extension meetings, field days, and Crop Diagnostic School and use tools including webinars, Twitter, and the telephone.

Weekly Update

Hello!

A special thanks ALWAYS to David Giffen (AAFC-Saskatoon) for all his work supporting the PPMN!  We are especially grateful this week for his keen eye!  David detected an issue with the incoming environmental data and, once again, steered us all in the right direction! 

Things are getting busy now for our field research programs so, from now until mid-July, the Weekly Update may need to be posted each week in portions at any point from Wednesday-Saturday.  Please bookmark the Blog or subscribe to receive the latest growing season information!

Please access the complete Weekly Update either as a series of Posts for Week 10 (June 13, 2019) OR a downloadable PDF. Be sure to check out the Insect of the Week – the rest of the growing season features doppelgangers to aid in-field scouting!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Meghan Vankosky or Jennifer Otani.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Subscribe to the Blog by following these easy steps!

Weather synopsis

This week there was an issue with the incoming environmental data but it was thankfully detected by David Giffen (AAFC-Saskatoon).  

A: TEMPERATURES – Temperatures continued to be cooler than average. This past week temperatures were coolest in AB and warmest in MB (Fig. 1). Average temperatures for May 12 to June 11, 2019, were approximately 1°C cooler than average (Fig. 2).   

Figure 1.  Average temperature (°C) across the Canadian prairies over the past SEVEN days (June 5-11, 2019).
Figure 2.  Average temperature (°C) across the Canadian prairies over the past 30 days (May 12-June 11, 2019).
Figure 3.  Percent of Average precipitation across the Canadian prairies for the growing season (April 1-June 13, 2019).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The growing degree day map (GDD) (Base 5 ºC, April 1-June 10, 2019) is below (Fig. 4):

Figure 4. Growing degree day (Base 5 ºC) across the Canadian prairies for the growing season (April 1-June 10, 2019).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The growing degree day map (GDD) (Base 10 ºC, April 1-June 10, 2019) is below (Fig. 5):

Figure 5. Growing degree day (Base 10 ºC) across the Canadian prairies for the growing season (April 1-June 10, 2019).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The lowest temperatures (°C) observed the past seven days are reflected in the map below (Fig. 6).

Figure 6. Lowest temperatures (°C) observed across the Canadian prairies the past seven days (June 7-13, 2019).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (13Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The highest temperatures (°C) observed the past seven days are reflected in the map below (Fig. 7).

Figure 7. Highest temperatures (°C) observed across the Canadian prairies the past seven days (June 7-13 2019).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

B: PRECIPITATION – During the past seven days, rainfall in central regions of AB and southern MB was reported to be greater than 15 mm (Fig. 8). Little or no rain was reported across central areas of SK. Rainfall totals for May 12-June 11 indicated that rainfall amounts were greatest in AB and MB (Fig. 9) while conditions continue to be very dry across most of SK (Fig. 10). 

Figure 8.  Cumulative precipitation (mm) across the Canadian prairies over the past SEVEN days (June 5-11, 2019).
Figure 9. Cumulative precipitation (mm) across the Canadian prairies over the past 30 days (May 12-June 11, 2019).

C: SOIL MOISTURE – Soil moisture values are low across most of the prairies (Fig. 10).

Figure 10. Modeled soil moisture (%) across the Canadian prairies (up to June 11, 2019).

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers can bookmark the AAFC Drought Watch Maps for the growing season.

Cutworms

Manitoba continues to experience cutworm issues this spring!  Thanks to John Gavloski (Manitoba Agriculture) who was able to provide a quick summary:

There has been a lot of insecticide applications and some reseeding of crops in Manitoba because of cutworms. Damage is to a variety of crops. Redbacked and dingy cutworms have been the two dominant species, although some other species of cutworms are being found. They are starting to turn to pupae, however stages are quite variable in some fields and scouting and insecticide applications continue.

Please refer back to our earlier Cutworm post (Wk05) for help with scouting and identification tips.  Also access the free downloadable Cutworm Field Guide.

Predicted bertha armyworm development

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.

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 new “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.

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!

Predicted grasshopper development

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper). 

This week, the grasshopper hatch is well underway across the prairies with most locations having 30% (12% last week) hatch and some areas are predicted to have hatch rates of 75%. Approximately 21% of the population is in the first instar (Fig. 1), 7% (2,5% last week) is predicted to be in the second instar (Fig. 2), and 1% in the third instar.  Grasshopper developmental rates are greatest across southern and central regions of SK. Over the past 30 days this region has experienced the warmest and driest conditions for the prairies. Recent, warm temperatures in southern MB has advanced grasshopper development. 

A survey of roadsides south of Saskatoon this week indicated that melanopline species were primarily first and second second instars.  

Figure 1.  Predicted percent of grasshopper (Melanoplus sanguinipes) population at first instar stage across the Canadian prairies (as of June 11, 2019). 
Figure 2. Predicted percent of grasshopper (Melanoplus sanguinipes) population at second instar stage across the Canadian prairies (as of June 11, 2019). 

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new “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.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9°C are produced using the Harcourt/North Dakota models (Soroka et al. 2015).  Models predicting the development of Alfalfa weevil (AAW) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. 

This past week warmer temperatures in southern MB advanced alfalfa weevil development. Weevils are predicted to be primarily in the second (53%) and third instars (22%) across most of southern areas in MB and SK (Fig. 1).

Figure 1. Predicted average instar stage of alfalfa weevil (Hypera postica)  acrossthe Canadian prairies as of June 11, 2019.

The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”.  The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9mm long.  

Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon).  Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide” (Philip et al. 2015). The guide is available in both a free English-enhanced or French-enhanced version.

Recap of earlier predicted model outputs

Last week, predictive model outputs were projected into June.  Please review the information for these insect pests by clicking the hyperlink:

Cabbage seedpod weevil

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.

Monitoring – Refer to the 2019 update of the PPMN Cabbage seedpod weevil monitoring protocol for detailed information, photos of all insect stages and canola damage:

  • Sample from the bud to flower stages in canola.  
  • 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.

Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.

Provincial Insect Pest Reports

Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information: 

• Manitoba‘s Insect and Disease Updates for 2019 are posted here and includes an update posted June 5, 2019.

• Saskatchewan‘s Crops Blog Posts includes a segment on “Early season scouting of cutworms” by Sara Doerksen posted in April 2019 and “Economic thresholds” by Kaeley Kindrachuk posted in May 2019.

•  Alberta Agriculture and Forestry’s Call of the Land regularly includes insect pest updates from Mr. Scott Meers. The most recent Call of the Land was posted March 18-22, 2019 but did not include an insect update.

Crop report links

Crop reports are produced by:

The following crop reports are also available:

Field Events – Speak to an entomologist

Public summer field events – Coming to a field near you –  Prairie field crop entomologists are already scheduled to be at these 2019 field tour events from May-August (be sure to re-confirm dates and details as events are finalized):

•  June 20, 2019: Solstice Forage and Crops Field Tour to be held at the Beaverlodge Research Farm (Beaverlodge AB).  View event info/registration details.  Entomologists tentatively participating: Jennifer Otani, Keith Uloth

•  June 26, 2019: 2019 CanolaPALOOZA to be held at the Lacombe Research and Development Centre (Lacombe AB).  View event info/registration details.  Entomologists tentatively participating: Jennifer Otani, Amanda Jorgensen, Meghan Vankosky, Scott Meers, Shelley Barkley, Patty Reid, Sunil Shivananjappa, Hector Carcamo, Julie Soroka, Mark Cutts, Jim Tansey, Sherrie Benson and the Junior Entomologists.

•  July 9-12, July 16-18, 2019: Crop Diagnostic School. Held at the University of Manitoba Research Farm at Carman, Manitoba. An 2-week diagnostic school will complete units on entomology, plant pathology, weed science, soil fertility, pulse crop production, and oilseed production. View registration and event information. Entomologists participating: John Gavloski and Jordan Bannerman.

•  July 9, 2019: CanolaPALOOZA Saskatoon, to be held at the SRDC Llewellyn Farm. Read more about this event.  Entomologists presenting: Tyler Wist, James Tansey, Greg Sekulic, Meghan Vankosky

•  July 22, 2019: Pulse grower gathering held near Three Hills AB.  Check Alberta Pulse Growers Event Page for more information.  Entomologists presenting: Graduate students from Dr. Maya Evenden’s (U of A) working on pea leaf weevil.

•  July 23-24, 2019: Crop Diagnostic School, Scott Saskatchewan. Read more about this event.  Entomologists presenting: Meghan Vankosky, Tyler Wist.

•  July 24, 2019: Crops-a-Palooza. Held at Canada-Manitoba Crop Diversification Centre (CMCDC), Carberry, Manitoba. Read more about this event. Entomologist participating: John Gavloski, Vincent Hervet, Tharshi Nagalingam, Bryan Cassone.

•  August 8, 2019:  2019 Wheatstalk to be held at Teepee Creek AB.  View event info/registration details.   Entomologists tentatively participating: Jennifer Otani, Amanda Jorgensen, Boyd Mori.

•  August 8, 2019. Horticulture School. Agriculture and Agri-Food Canada Research Farm, Portage la Prairie, Manitoba. View event info/registration details.  Entomologist presenting: John Gavloski, Kyle Bobiwash.

Monarch migration

We continue to track the migration of the Monarch butterflies as they move north by checking the 2019 Monarch Migration Map!  A screen shot of the map has been placed below as an example (retrieved 14Jun2019) but follow the hyperlink to check the interactive map.  They are moving further north and west in Manitoba!

Visit the Journey North website to learn more about migration events in North America and visit their monarch butterfly website for more information related to this amazing insect.  

Previous Posts

Click to review these earlier 2019 Posts: 

  ● 2019 Risk and forecast maps – Week 2

 ● Cereal Aphid Manager APP – Week 9
   ● Cereal leaf beetle – Week 9
   ● Crop protection guides – Week 6
   ● Cutworms – Week 5

  ● Field heroes – Week 6
   ● Flea beetles – Week 5

  ● Insect scouting chart for Canola – Week 5
   ● Insect scouting chart for Flax – Week 5

  ● Pea leaf weevil – Week 9
   ● Painted lady butterfly – Week 8

  ● Ticks and Lyme disease – Week 4

  ● Weather Radar – Week 6
   ● Wildfires – Week 8
   ● Wind trajectories – Weeks 1-4

Doppelgangers: Bertha armyworm and clover cutworm

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

To learn more about bertha armyworms and clover cutworms, go to the Insect of the Week page or download copies of the Field Crop and Forage Pests andtheir Natural Enemies in Western Canada and Cutworm Pests of Crops onthe Canadian Prairies identification field guides.

Wind Trajectories

Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s.

In a continuing effort to produce timely information, the wind trajectory reports are available in two forms:

Prairie Crop Disease Monitoring Network

The Prairie Crop Disease Monitoring Network (PCDMN) represents the combined effort of our prairie pathologists who work together to support in-field disease management in field crops.  

In 2019, the PCDMN will release a series of weekly Cereal Rust Risk Reports throughout May and June.  Information related to trajectory events based on forecast and diagnostic wind fields and cereal rust risk is experimental, and is OFFERED TO THE PUBLIC FOR INFORMATIONAL PURPOSES ONLY. 

Background:  Agriculture and AgriFood Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth. In addition, plant pathologists have shown that trajectories can assist with the prediction of plant disease infestations and are also beginning to utilize these same data. An introduction will be presented of efforts to identify wind trajectory events that may bring rust urediniospores into Western Canada from epidemic areas in the central and Pacific northwest (PNW) regions of the USA. Identification of potential events as well as an assessment of epidemic severity from source locations, and prairie weather conditions, will be used to assess the need for prompt targeted crop scouting for at-risk regions of the Canadian Prairies.

This week, two documents are available from the PCDMN:

Summary of wind trajectory and cereal rust risk assessment and the need for in-crop scouting in the Prairie region, June 4-10, 2019:

1. Pacific Northwest – Currently there is limited stripe rust development in the PNW, a moderate-high number of recent wind trajectories from the PNW, relatively dry Prairie weather conditions, and generally early stages of Prairie crop development, especially in spring cereals.  Thus, as of June 10, 2019, the risk of stripe rust appearance from the PNW is relatively low and scouting for this disease is not urgent.  

2. Texas-Oklahoma corridor –In general, crops are advancing towards maturity, while in many areas of Texas harvesting has been completed, and thus will become less of a source of rust inoculum.  There has been a limited number of recent wind trajectories from this area, relatively dry Prairie weather conditions, and generally early stages of Prairie spring crop development.  Thus, as of June 10, 2019, the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is low and scouting for these diseases is not urgent.  

3. Kansas-Nebraska corridor –Leaf and stripe rust development in winter wheat continues in Kansas, although the winter crop is starting to turn colour in some regions.  Although rusts have only been recently reported in Nebraska, levels are on the rise, and thus over the next few weeks this region could act as a significant source of rust inoculum for the Prairie region.  From June 4-10, 2019 there has been a low-moderate number of wind trajectories from this area.  In general, weather conditions have been relatively dry across the Prairies with generally early stages of Prairie crop development depending on the region.  Thus, as of June 10, 2019, the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is relatively low and scouting for these diseases is not urgent; however, further development of rust in these regions, especially Nebraska, may increase the risk.  

4. Where farmers or consultants noticed stripe rust development on winter wheat in the fall of 2018, it is recommended to scout winter wheat fields this spring.  Scouting is especially critical where the variety being grown is susceptible to stripe rust.  Currently, there are no reports of stripe rust in commercial fields of winter or spring wheat across the Prairie region.

5.  Access the full downloadable report.

Insect of the Week – Natural enemies of pea aphids

Populations of pea aphids, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), can be kept below the economic threshold by their natural enemies if these are present early and in sufficient numbers. Natural enemies include parasitoids, predators, and diseases that reduce pest populations.

Predators of pea aphids include ladybird beetles (adults and larvae), syrphid fly larvae, and damsel bugs. These predators catch and eat pea aphids of all ages and sizes. They are classified as generalists because they also prey on other insect species.

The many faces of the adult harlequin ladybeetle 
 (aka multicoloured Asian ladybeetle) (Photo: ©Entomart)
Harlequin ladybeetle larva (Photo: cc by-sa Quartl)

Pea aphids are attacked by several species of parasitoid, including Aphidius ervi Haliday (Hymenoptera: Aphidiidae: Aphidiinae). Female parasitoids lay individual eggs inside aphid nymphs. After hatching, the parasitoid larva consumes its host, eventually killing it. The parasitoid pupates inside the dead or mummified aphid before a new adult parasitoid emerges.

Aphid mummies look bloated and discoloured compared to healthy adult aphids. Parasitism rates can be estimated by counting the number of aphid mummies on five host plants at five locations within a field.

Aphidius ervi parasitoid (Photo: cc by Penny Greeves)

For more information about the predators and parasitoids of pea aphids, visit the Insect of the Week page or consult Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide.

To learn more about some of the natural enemies fighting pests in background for free, go to www.fieldheroes.ca or follow @FieldHeroes on Twitter.

Blog post submitted by Dr. Meghan Vankosky.
Follow her at @Vanbugsky.

Weekly Update

Greetings!

Field crop entomologists across the prairies are again surveying so the Weekly Update is restricted to the basics for Week 10.

Access the Weekly Update as a series of Posts for Week 10 (July 12, 2018). A similarly abridged downloadable PDF is available.   Review the “Insect of the Week” for Week 10!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Meghan Vankosky or Jennifer Otani.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Subscribe to the Blog by following these three steps!

Weather synopsis

Weather synopsis – This week staff were again surveying so we direct you to the AAFC Drought Watch maps in addition to the following updates.

This past week (July 2 – 9, 2018), temperatures across the prairies were warmer than long term average values (Fig. 1). The warmest weekly temperatures continue to occur across Manitoba. Compared to last week, daily average temperatures were warmer across southern Alberta and Saskatchewan. The 30-day (June 9  – July 9, 2018) average temperature was similar to the long term average. 

Figure 1. Weekly (July 2 – 9, 2018) average temperature (°C).

Weekly and 30-day total precipitation was slightly above average (Figs. 2 and 3).  Weekly accumulations were generally less than 20 mm with a few areas (northeast Saskatchewan, northwest Manitoba and the south of the Peace River region) reporting greater than 40 mm. The wettest (30-day) regions were across eastern areas in Saskatchewan, and isolated areas in southern Manitoba and the south of the Peace River region. A large region across Saskatchewan and Alberta continues to be dry.

Figure 2. Weekly (July 2 – 9, 2018) cumulative precipitation (mm).
Figure 3. The 30-day (June 9 – July 9, 2018) cumulative precipitation (mm).

The growing degree day map (GDD) (Base 10ºC, March 1 – July 8, 2018) is below:

The growing degree day map (GDD) (Base 5ºC, March 1 – July 9, 2018) is available below:

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers may wish to bookmark the AAFC Drought Watch Maps for the growing season.

Wheat midge

Wheat Midge (Sitodiplosis mosellana) – As of July 9, 2018, the model runs indicate that wheat midge oviposition is well underway across a large area of Manitoba and Saskatchewan.  Populations in this region are primarily in the egg stage (Fig. 1) with larvae appearing as well. 

Figure 1. Percent wheat midge in the egg stage based on model simulations for April 1 – July 9, 2018.

Monitoring:

When monitoring wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (photographed by AAFC-Beav-S. Dufton & A. Jorgensen below). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (photographed by AAFC-Beav-S. Dufton below), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember your insecticide control options for wheat midge also kill these beneficial insects which help reduce midge populations.

Economic Thresholds for Wheat Midge:

a) To maintain optimum grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.

b) For yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.

Inspect the developing kernels for the presence of larvae and the larval damage. 

Click here to review the 2018 wheat midge forecast map.  

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  Additionally, more information can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted grasshopper development

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).  

As of July 9, 2018, the grasshopper model output indicates that development is approximately 10 days ahead of normal with populations consisting of 4th and 5th instar stages and adults.  The most rapid grasshopper development occurred across southern and central regions (Fig. 1). 

Figure 1.  Grasshopper development (average instar) based on model simulations, for April 1 – July 9, 2018.

Grasshopper Scouting Steps: 

● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.

● Starting at one end in either the field or the roadside and walk toward the other end of the 50 m making some disturbance with your feet to encourage any grasshoppers to jump. 

● Grasshoppers that jump/fly through the field of view within a one meter width in front of the observer are counted. 

● A meter stick can be carried as a visual tool to give perspective for a one meter width.  However, after a few stops one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance. 

● At the end point the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure. 

● Compare counts to the following damage levels associated with pest species of grasshoppers:

0-2  per m² – None to very light damage

2-4  per m² – Very light damage

4-8  per m² – Light damage

8-12 per m² – Action threshold in cereals and canola

12-24 per m² – Severe damage 

>24 per m² – Very severe damage

* For lentils at flowering and pod stages, >2 per m² will cause yield loss.

* For flax at boll stages, >2 per m² will cause yield loss.

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new “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.

Lygus in canola

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.

Abundant parastioids in canola!

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).

Learn more about beneficials by accessing Field Heroes and all the Blog’s Parasitoid posts.

Download the Field Guide

If you haven’t downloaded the FREE field guide yet, please do so now!

Field Crop and Forage Pests and their Natural Enemies in Western Canada: IDENTIFICATION AND MANAGEMENT FIELD GUIDE

The 152-page, full-colour field guide, now available online, is designed to help you make informed decisions in managing over 90 harmful pests of field and forage crops in Western Canada. Better decision making helps save time and effort and eliminates unnecessary pesticide applications to improve your bottom line. The guide also helps the reader identify many natural enemies that prey on or parasitize pest insects. Recognizing and fostering populations of natural enemies will enhance their role in keeping or reducing pest populations below economic levels.

Find links to download the FREE Insect Field Guide.

Previous Posts

The following is a list of 2018 Posts – click to review:

Alfalfa weevil – Week 6

Bertha armyworm – Week 9

Cabbage seedpod weevil – Week 8 
Cereal aphid manager (CAM) – Week 2
Cereal leaf beetle – Week 5
Cereal leaf beetle larvae request – Week 8
Crop protection guides – Week 2
Crop reports – Week 8
Cutworms – Week 4

Diamondback moth – Week 7

Field heroes – Week 8
Flea beetles – Week 4

Monarch migration – Week 8

Pea leaf weevil – Week 8
PMRA Pesticide Label Mobile App – Week 4

Scouting charts (canola and flax) – Week 3

Ticks and Lyme Disease – Week 4

Weather radar – Week 3
West nile virus – Week 8
Wind trajectories – Week 6
Wireworm distribution maps – Week 6
White grubs in fields – Week 8

Provincial Insect Pest Reports

Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information: 

Manitoba‘s Insect and Disease Updates for 2018 can be accessed here. Issue #6 (posted July 4, 2018) included reports of grasshoppers, low numbers of aphids in peas and cereal crops, and importance of protecting and preserving pollinators in any flowering crop.

Saskatchewan‘s Crop Production News for 2018 is posted with Issue #4 now available. This issue includes a report from the Crop Protection Lab summarizing disease and insect samples submitted this growing season. Saskatchewan growers can review articles on how to scout for cutworms, how to assess plant stand densities in flax or canola, and for flea beetles, pea leaf weevils. Also note the following diamondback moth pheromone trap interception counts from across the regions (updated June 27, 2018):

Alberta Agriculture and Forestry’s Call of the Land regularly includes insect pest updates from Scott Meers. The most recent Call of the Land (posted July 12, 2018) identified that SOME bertha armyworm pheromone traps over a wide geographic range have started to intercept higher numbers of moths. This means in-field scouting will be critical in 10-14 days (as larvae move up from leaves to feed among canola pods). Processing of canola survey samples has begun; initial samples suggest lower diamondback moth and Lygus bug numbers so far compared to 2017 but higher numbers of small parasitoid wasps associated with diamondback moths, and a pocket of grasshoppers (clearwinged) near Carmangay AB.

Cabbage seedpod weevil

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.


Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.

Also watch provincial reports for updates on surveying underway now.  Alberta Agriculture & Forestry has posted a live CSPW map and online reporting tool for growers.  A screenshot (retrieved 06Jul2017) is included below.

Crop reports

Crop reports are produced by:
• Manitoba Agriculture, Rural Development (July 4, 2017)
• Saskatchewan Agriculture Crop Report (June 27-July 3, 2017)

• Alberta Agriculture and Forestry Crop Report (June 27, 2017)

Provincial Insect Pest Reports

Provincial entomologists provide insect pest updates throughout the growing season so we have attempted to link to their most recent information: 


● Manitoba’s Insect and Disease Update for 2017 is prepared by John Gavloski and Pratisara Bajracharya and read Issue #7 (posted July 5, 2017) noting the presence of thistle caterpillar (Vanessa cardui) and larval populations of diamondback moth reaching economically significant levels in the southwest of that province. Cumulative counts of bertha armyworm generated from weekly counts in Manitoba can be accessed here.

● Saskatchewan’s Crop Production News – 2017 – Issue #3 includes the insect update prepared by Scott Hartley and Danielle Stephens. That report includes an update on the red bugs in canola (also described in Week 8) and how to submit samples to that provincial lab, very low numbers of diamondback moth in pheromone traps across that province, initial low numbers of bertha armyworm in pheromone traps, and cabbage seedpod weevil.


● Watch for Alberta Agriculture and Forestry’s Call of the Land and access the most recent Insect Update (July 5, 2017) provided by Scott Meers. That report notes migration of painted lady butterflies which feed on thistles but also soybeans, sunflowers, and dry beans. Soybean and sunflower producers will need to carefully follow the development of a second generation of V. cardui as it could affect those crops by mid-July. Additionally, diamondback moth are more numerous than in previous seasons so careful scouting will be required during early pod stages in canola as that stage is the most susceptible to yield losses.

Insect of the Week – Aphidius parasitoid wasp

This week’s Insect of the Week is the Aphidius parasitoid wasp. Their hosts include over 40 species of aphids. Egg to adult development occurs inside the host. New adults chew a hole in the mummified aphid to exit and immediately search for new aphid hosts.

For more information on the Aphidius parasitoid wasp, see our Insect of the Week page.

Parasitized English grain aphid (Tyler Wist, AAFC)
Aphidiidae – adult (Aphidius avenaphis) (Tyler Wist, AAFC)

Follow @FieldHeroes to learn more about the natural enemies that are working for you for FREE to protect your crops!

Remember the NEW Cutworm Field Guide is free and downloadable in 2017!

Weekly Update – Greetings!

Greetings!

Please access the Weekly Update for July 6, 2017 (Week 10), as either a series of Posts for Week 10 (Jul 06, 2017) or a downloadable PDF.   


Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Owen Olfert or Jennifer Otani.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Subscribe to the Blog by following these easy steps!

Weekly Update – Weather Synopsis

Weather synopsis – This past week, average temperatures were slightly below long-term normals for mid-June.  Average temperatures for June indicate that Alberta temperatures were average, to above average, while Saskatchewan was slightly below than average temperatures. 







Total 30 day rainfall accumulations indicate that conditions are dryer than normal for most of Saskatchewan, the southern Peace River region and large areas of Manitoba.  Central and southern Alberta has had normal rainfall for June.



The lowest temperatures across the prairies over the past seven days (June 29-July 5, 2017) are mapped below.  


In contrast, the highest temperatures recorded over the past seven days (June 29-July 5, 2017) are presented below.  

The updated growing degree day map (GDD) (Base 5ºC, March 1 – July 3, 2017) is below:



While the growing degree day map (GDD) (Base 10ºC, March 1 – July 3, 2017) is below:


The maps above are all produced by Agriculture and Agri-Food Canada.  Growers may wish to bookmark the AAFC Drought Watch Maps for the growing season.

Weekly Update – Predicted Bertha Armyworm Development

Bertha armyworm (Lepidoptera: Mamestra configurata) – Bertha armyworm should be in the adult stage across the prairies this week.  The map illustrates predicted appearance of adults (percent of the population) across the southern prairies.

For those monitoring BAW pheromone traps, compare trap “catches” to the following reference photo kindly shared by Saskatchewan Agriculture:



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 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.

Weekly Update – Wheat midge

Wheat Midge (Sitodiplosis mosellana) – Reminder – The previous Insect of the Week (Week 7) features wheat midge!  

Simulation modelling is used to predict wheat midge emergence across the Canadian prairies.  Predicted adult emergence for Saskatoon and Melfort is very similar to last week.  Elliott et al. (2009) reported that adult emergence was affected by inadequate rainfall amounts (May and June). The model was parameterized to take rainfall into account.  Output indicates that emergence at Saskatoon has been limited by inadequate rainfall during June. Rainfall for Saskatoon in June was 37 mm compared to long-term average of 61 mm.  Emergence at Melfort is predicted to be more advanced. June rainfall was 61 mm. 





Monitoring:
When monitoring wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (photographed by AAFC-Beav-S. Dufton & A. Jorgensen below). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.


REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (photographed by AAFC-Beav-S. Dufton below), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember your insecticide control options for wheat midge also kill these beneficial insects which help reduce midge populations.




Economic Thresholds for Wheat Midge:

a) To maintain optimum grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.

b) For yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.

Inspect the developing kernels for the presence of larvae and the larval damage. 



Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

NEW – Alberta Agriculture and Forestry has also released a YouTube video describing in-field monitoring for wheat midge this week.  


More information about Wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Weekly Update – Predicted Grasshopper Development

Grasshopper Simulation Model Output – Based on model output, grasshopper development is very similar to long-term averages.  Across the prairies, grasshoppers should be predominantly in the second and third instar stages with more rapid development across southern Alberta. The greatest development was predicted to be across all of the southern regions.

Grasshopper Scouting Steps: 

● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.

● Starting at one end in either the field or the roadside and walk toward the other end of the 50 m making some disturbance with your feet to encourage any grasshoppers to jump. 

● Grasshoppers that jump/fly through the field of view within a one meter width in front of the observer are counted. 

● A meter stick can be carried as a visual tool to give perspective for a one meter width.  However, after a few stops one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance. 

● At the end point the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure. 
● Compare counts to the following damage levels associated with pest species of grasshoppers:

0-2  per m² – None to very light damage
2-4  per m² – Very light damage
4-8  per m² – Light damage
8-12 per m² – Action threshold in cereals and canola

12-24 per m² – Severe damage 
>24 per m² – Very severe damage


* For lentils at flowering and pod stages, >2 per m² will cause yield loss.
* For flax at boll stages, >2 per m² will cause yield loss.

Reminder:  Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Food and Rural Development, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new “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.

Weekly Update – Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Across the prairies, the model indicates that 80% of the population should be in the pupal stage. Adults should be appearing near Saskatoon this week.





In terms of degree-day heat units, the map below reflects the predicted development of alfalfa weevil across the Canadian prairies.



Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide” (Philip et al. 2015).  That guide is available in both a free English-enhanced or French-enhanced version.

Weekly Update – Monarch migration

We again track the migration of the Monarch butterflies as they move north by checking the 2017 Monarch Migration Map!  A screen shot of the map has been placed below as an example (retrieved 06Jul2017) but follow the hyperlink to check the interactive map! 

Weekly Update – Previous Posts

The following is a list of 2017 Posts – click to review:

Bertha armyworm (Week 9)
Brood X Cicadas

Cabbage seedpod weevil (Week 8)
Canola scouting chart
Cereal leaf beetle
Crickets with your popcorn
Crop protection guides
Crop reports (Week 8)
Cutworms

Diamondback moth

Flax scouting chart
Flea beetles

Grasshopper development (Week 8)

Iceberg reports

Lily leaf beetle


Painted lady butterflies (Week 9)
Pea leaf weevil
PMRA Pesticide Label Mobile App
Provincial Insect Pest Reports (Week 8)

Nysius niger (Week 8)

Ticks and Lyme disease

Weather radar

Wind trajectories

Cabbage seedpod weevil

Cabbage seedpod weevil (Ceutorhynchus obstrictus) –  Reminders for 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.



Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.

Also watch provincial reports for updates on surveying underway now.  Alberta Agriculture & Forestry has released a new live CSPW map and online reporting tool for growers.  A screenshot (retrieved 06 Jul 2016) is included below.

Provincial Insect Pest Reports

Provincial entomologists provide insect pest updates throughout the growing season so we have attempted to link to their most recent information: 

– Manitoba’s Insect and Disease Update (July 4, 2016,
prepared by John Gavloski and Pratisara Bajracharya).
– Saskatchewan’s Insect Report which mentions redbacked cutworms
but emphasizes scouting for cabbage seedpod weevil, wheat midge and
grasshoppers (Issue 4,
prepared by Scott Hartley).

– Watch for Alberta Agriculture and Forestry’s Call of the Land for
updates from Scott Meers who recently provided an update (posted on July 7, 2016). 

Insect of the Week – Bertha armyworm parasitoids

Bertha armyworm parasitoids – Ichneumonids and Tachinids


Last year, the focus of the Insect of the Week was crop pests. This year, we’re changing things up and highlighting the many natural enemies that help you out, silently and efficiently killing off crop pests. [note: featured Insects of the Week in 2015 are available on the Insect of the Week page] 

This week’s Insects of the Week are tachinids, and ichneumonidae. The adult tachinid will feed on flower nectar, honeydew from aphids, scales, and mealybugs. The tachinid, Athrycia cinerea (Coq.), is a parasitoid of the Bertha armyworm. Ichneumonidae adults also eat nectar and aphid honeydow, however, its larvae (Banchus flavescens, Cresson) are parasitoids of Lepidoptera, Coleoptera, Diptera, Hymenoptera, and some spiders. 

For more information about these parasitoids, the other pests they control and other important crop and forage insects, see the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide for identification, life cycle and conservation options (download links for field guide available on the Insect of the Week page).

Ichneumonid – adult (Banchus flavescens). © John Gavloski, Manitoba Agriculture

Tachinid- adult. © Alberta Agriculture and Rural Development


Weekly Update

This week, Staff at Saskatoon and Beaverlodge are surveying.  The Weekly Update will be available Friday morning.

Tip: If we’re surveying in fields, you should be too!

Weekly Update

Greetings!


All our Staff are surveying
so a brief version of the Weekly Update is provided for the week of July 6th!

A downloadable PDF version of the complete Weekly Update for Week 10 (July 6, 2016) can be accessed here.  

This edition includes the “Insect of the Week” featuring beneficial arthropods in 2016!

Subscribe to the Blog by following the instructions posted here!  You can receive automatic updates in your inbox through the growing season.



Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Owen Olfert or Jennifer Otani.  Past “Weekly Updates” are very kindly archived to the Western Forum website by webmaster, Dr. Kelly Turkington.  

Weekly Update – Weather Synopsis

Staff are busy surveying so some maps are not available this week.

The map below reflects the Accumulated Precipitation for the Growing Season so far for the prairie provinces (i.e., May 1-June 30, 2016):



The updated growing degree day map (GDD) (Base 5ºC, March 1 – July 3, 2016) is below:



While the growing degree day map (GDD) (Base 10ºC, March 1 – July 3, 2016) is below:



The maps above are all produced by Agriculture and Agri-Food Canada.  Growers may wish to bookmark the AAFC Drought Watch Maps for the growing season.

Weekly Update – Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Please refer to earlier posts to find information related to the appearance, damage and biology of this insect pest.  



Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models.  The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur.  Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.




For the week of July 3, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days.  Areas highlighted orange are predicted to find fourth instar larvae.



Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities.

In hay fields, forage losses can be economic if one or more of the following symptoms are noted:
● if 25-50 % of the leaves on the upper one-third of the stem show damage, or
● if 50-70% of the terminals are injured, or
● if 1 to 3 third or fourth instar larvae occur per stem (with shorter stems having lower economic thresholds and 3 or more larvae requiring treatment no matter what the alfalfa height), or 
● 20-30 larvae per sweep occur when 12% leaf loss is acceptable.
● Also consider these two points:
      1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations.
      2. If the hay crop value is high and weevil injury is seen or 2 or more larvae per stem reappear in regrowth after cutting, insecticide may be necessary (if a second cut is anticipated). 

In alfalfa seed fields:
● Economic thresholds are 20-25 third to fourth instar larvae per sweep or 35-50% of the foliage tips showing damage. 
● Thresholds increase with the height of the alfalfa, and decrease in drought conditions. 
● Also know that several small wasps parasitize alfalfa weevil larvae and adults, and in the past these natural control agents kept the weevil in check in most years. One of these wasps, Bathyplectes curculionis (Thomson), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.

Weekly Update – Cereal leaf beetle

Cereal leaf beetle (Oulema melanopus) – Reminder – Please refer to earlier posts for information
related to the biology, damage and monitoring of the Cereal leaf beetle.


Cereal leaf beetle larvae hatch from eggs in about 5 days and feed for about 3 weeks, passing through 4 growth stages (instars). The head and legs are brownish-black; the body is yellowish. Larvae are usually covered with a secretion of mucus and fecal material, giving them a shiny black, wet appearance (Fig. 1).  When the larva completes its growth, it drops to the ground and pupates in the soil.  The pupal stage lasts 2 – 3 weeks. Adult beetles emerge and feed for a couple of weeks before seeking overwintering sites. There is one generation per year.

Figure 1.  Larval stage of Oulema melanopus with characteristic feeding damage visible on leaf.


Monitoring:
Give priority to following factors when selecting monitoring sites:
   □ Choose fields and sections of the fields with past or present damage symptoms.
   □ Choose fields that are well irrigated (leaves are dark green in color), including young, lush crops. Areas of a field that are under stress and not as lush (yellow) are less likely to support CLB. 
   □ Monitor fields located along riparian corridors, roads and railroads. 
   □ Survey field areas that are close to brush cover or weeds, easy to access, or are nearby sheltered areas such as hedge rows, forest edges, fence lines, etc.

Focus your site selection on the following host plant priorities:
   □ First – winter wheat. If no winter wheat is present then;
   □ Second – other cereal crops (barley, wheat, oats, and rye). If no cereal crops are present then;
   □ Third – hay crops. If no hay crops or cereal crops are present then;
   □ Fourth – ditches and water corridors
Sweep-net Sampling for Adults and Larvae:
 ● A sweep is defined as a one pass (from left to right, executing a full 180 degrees) through the upper foliage of the crop using a 37.5 cm diameter sweep-net. 
 ● A sample is defined as 100 sweeps taken at a moderate walking pace collected 4-5 meters inside the border of a field.  
 ● At each site, four samples should be collected, totaling 400 sweeps per site.  The contents of each sample should be visually inspected for life stages of CLB and all suspect specimens should be retained for identification.  
 ● Because the CLB larvae are covered in a sticky secretion, they are often covered in debris and are very difficult to see within a sweep-net sample. 
 ● To help determine the presence of CLB, place the contents of the sweep net into a large plastic bag for observation.

Visual Inspection:
Both the adults and larvae severely damage plants by chewing out long strips of tissue between the veins of leaves (Fig. 1), leaving only a thin membrane. When damage is extensive, leaves turn whitish. 

Fact sheets for CLB are published by the province of Alberta and available from the Prairie Pest Monitoring Network. Also access the Oulema melanopus page from the new “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide”.

Weekly Update – Previous Posts

The following is a list of previous 2016 Posts – click to review:


Crop reports

Cereal leaf beetle
Bertha armyworm development and flight
Grasshoppers
Swede midge
Canola scouting chart
Wind trajectories
Cutworms
Flea beetles in canola
Predicted cereal leaf beetle development
Predicted lygus bug development
Predicted wheat midge development
Pea leaf weevil monitoring
Crop protection guides
Using Environment Canada’s radar maps to follow precipitation events
Iceburg reports
Multitude of mayflies

Monarch migration

Weekly Update – Wheat midge

Wheat Midge (Sitodiplosis mosellana) – Predictive modelling will be used again to help  forecast wheat midge emergence across the Canadian prairies.  The map below predicts the geographic distribution and corresponding accumulation of heat units necessary for wheat midge to emerge from puparia developing in the soil.  

Insect of the Week – Blister beetles

The blister beetle (Lytta nuttalli Say and Epicauta spp.)  is this week’s Insect of the Week  (from the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide – download links available on the Insect of the Week page).