Tag: 2020Jul16

Weather synopsis

The 2020 growing season, April 1 – July 12, 2020, has been cooler and wetter than normal across many locations in Alberta and Saskatchewan. Conditions in Manitoba have been warmer and dryer than normal. This past week (July 6-12, 2020) prairie temperatures were warmest in Manitoba and eastern Saskatchewan (Table 1; Fig. 1). Average 7-day temperatures continue to be warmest across Manitoba and eastern Saskatchewan and coolest across most of Alberta (Table 1; Fig. 1).

**Figure 1.** Observed average temperatures across the Canadian prairies the past seven days (July 6-12, 2020).

Average 30-day (June 13-July 12, 2020) temperatures continue to be cooler in Alberta than in southern Saskatchewan and Manitoba (Table 2; Fig. 2). The average 30-day temperature at Winnipeg and Brandon continued to be greater than locations in Alberta and Saskatchewan (Fig. 2). Temperature anomalies indicate that temperatures have been below normal across most of Alberta and Saskatchewan and were 0 to 2 °C warmer than average across eastern Saskatchewan and southern Manitoba (Table 2; Fig. 3). Based on growing season temperatures (April 1 – July 12, 2020), conditions have been warmest for southern locations (Table 3).

**Figure 2.** Observed average temperatures across the Canadian prairies the past 30 days (June 13-July 12, 2020).

**Figure 3**. Mean temperature difference from Normal the past 30 days (June 16-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (13Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

Cumulative rainfall for the past 7 days was lowest across southern regions of Alberta and across most of Manitoba (Table 1 Fig. 4). Lethbridge reported 4.2 mm and Winnipeg reported 1.4 mm (Table 1). Cumulative 30 day rainfall continued to be greatest across central regions of Alberta (Table 2; Fig. 5). Rainfall amounts were lowest across southern regions of the prairies (Table 2; Fig. 5).

**Figure 4**. Observed cumulative precipitation across the Canadian prairies the past seven days (July 6-12, 2020).

Total 30-day rainfall at Brandon, Winnipeg and Swift Current was less than 100 mm (Table 2; Fig. 5). Lethbridge has reported 122.3 mm (261% of normal) in the past 30 days (Table 2). Growing season rainfall (percent of average) is below normal across eastern Saskatchewan and localized areas of Manitoba.

**Figure 5**. Observed cumulative precipitation across the Canadian prairies the past 30 days (June 13-July 12, 2020).

**Figure 6.** Percent of average precipitation for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 5 ºC, April 1-July 13, 2020) is below (Fig. 7):

**Figure 7**. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 10 ºC, April 1-July 13, 2020) is below (Fig. 8):

**Figure** 8. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The highest temperatures (°C) observed the past seven days ranged from <15 to >33 °C in the map below (Fig. 9).

**Figure 9**. Highest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

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

Predicted bertha armyworm development

Model simulations for July 12, 2020 indicate that 35% of the population is in the egg stage (37% last week) and 65% of the population is in the larval stages (14% last week). Across the Parkland and Peace River regions, BAW populations are predicted to be primarily in the egg stage (Fig. 1). Populations across southern regions are primarily in the larval stage (Fig. 1).

**Figure 1**. Predicted percent of bertha armyworm (*Mamestra configurata*) population ***in the larval stage*** as of July 12, 2020.

The two graphs below demonstrate that larval development near Brandon is predicted to be ahead of fields near Grande Prairie. In Brandon, populations are primarily in the larval stage (Fig. 2) while BAW populations near Grande Prairie are predicted to be predominantly in adult and egg stages (Fig. 3).

**Figure 3**. Predicted bertha armyworm (*Mamestra configurata*) phenology at Brandon MB as of July 12, 2020.

**Figure 3**. Predicted bertha armyworm (*Mamestra configurata*) phenology at Grande Prairie AB as of July 12, 2020.

**Figure 5**. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).

Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba (as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is how the economic threshold is applied to manage this pest.

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images above (Fig. 5) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

Wheat midge model runs indicate that, where wheat midge are present, adult emergence is well underway and oviposition is occurring across most prairie locations. The map suggests that, as of July 12, 2020, populations are primarily in the egg stage (Fig. 1). Low rainfall amounts across large areas of Manitoba and Saskatchewan has resulted in delayed adult emergence, resulting in lower egg densities.

**Figure 1**. Predicted percent of population of wheat midge (*Sitodiplosis mosellana*) at adult stage across the Canadian prairies (as of July 12, 2020).

The next 10-14 days are very important for monitoring wheat midge populations for the purpose of making management decisions. Simulations were run to July 26 to assess population development over the next 10 days (Table 1). The following table indicates that 50% emergence of adults should occur this week at Saskatoon and next week at Lacombe (Table 1). This week populations in Manitoba are predicted to be at 90% adult emergence (Table 1).

The two graphs below illustrate the development of wheat midge populations near Saskatoon (Fig. 2) and Lacombe (Fig. 3). Adult numbers are currently peaking near Saskatoon while adult emergence near Lacombe is not expected to peak until next week.

**Figure 2**. Predicted wheat midge (*Sitodiplosis mosellana*) phenology at Saskatoon SK *projected to July 21, 2020*.

**Figure 3**. Predicted wheat midge (*Sitodiplosis mosellana*) phenology at Lacombe AB *projected to July 21, 2020*.

The next two graphs compare the synchrony between wheat midge and wheat for fields near Lacombe (Fig. 4). The graph indicates that peak adult emergence and oviposition may occur during anthesis; wheat susceptibility decreases once the crop is flowering (Fig. 4).

**Figure 4**. Comparison of predicted phenology of wheat midge (*Sitodiplosis mosellana*) and wheat at Lacombe AB projected to July 21, 2020.

The last graph compares phenology (Saskatoon) of wheat midge adults with Macroglenes penetrans, a parasitoid of wheat midge (Fig. 5). The parasitoid wasp lays eggs in wheat midge eggs. The graph shows that emergence/oviposition of wheat midge adults and M. penetrans are similar (Fig. 5). This information can be used as a guide to determine when fields should be monitored.

**Figure 5**. Comparison of predicted phenology of wheat midge (*Sitodiplosis mosellana*) and its parasitoid, *Macroglenes penetrans*, at Saskatoon SK *projected to July 21, 2020*.

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

As of July 12, 2020, the grasshopper model estimates that development across the prairies ranges from 1st instar stage to adults. Based on the model simulations, development has been slowest in the Peace River region where average nymph development ranges between the 2nd and 3rd instars (Fig. 1; Table 1). Across the southern prairies, the majority of the nymph population is predicted to be in the 3rd to 5th instar stages, with adults predicted to occur across southern Manitoba where populations are active (Fig. 1; Table 1). Across the prairies, populations are predicted to be 6, 6, 11, 27, 24, 21 and 5% in egg, first, second, third, fourth, fifth and adult stages, respectively.

**Figure 1**. Predicted average instar stages of grasshopper (*Melanoplus sanguinipes*) populations across the Canadian prairies (as of July 12, 2020).

Table 1 indicates that predicted development at Brandon and Winnipeg is well ahead of Lacombe and Grande Prairie. The two graphs compare grasshopper development in Saskatoon (Fig. 2) and Winnipeg (Fig. 3). Grasshopper populations near Saskatoon are predominantly in the 4th and 5th instars with first appearance of adults beginning to occur (Fig. 2). Populations near Winnipeg are expected to be primarily adults (Fig. 3).

**Figure 2**. Predicted grasshopper (*Melanoplus sanguinipes*) phenology at Saskatoon SK. Values are based on model simulations (April 1-July 12, 2020).

**Figure** 3. Predicted grasshopper (*Melanoplus sanguinipes*) phenology at Winnipeg MB. Values are based on model simulations (April 1-July 12, 2020).

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 “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (Philip et al. 2018) as an English-enhanced or French-enhanced version.

Lygus bug monitoring

On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.

Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.

**Figure 1**. Adult *Lygus lineolaris* (5-6 mm long) (photo: AAFC-Saskatoon).

**Figure 2**. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field. Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3).

**Figure 3**. Sequential sampling for lygus bugs at late flowering stage in canola.

If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).

The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop.

Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production. The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage. In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.

How to tell them apart: The 2019 Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids! Both posts include tips to to discern the difference between when doing in-field scouting!

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol. Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.

Field heroes

The Field Heroes campaign continues to raise awareness of the role of beneficial insects in western Canadian crops. Check the recently updated Field Heroes website for scouting guides, downloadable posters, and videos. Learn about these important organisms at work in your fields!

Real Agriculture went live in 2020 with a Pest and Predators podcast series!

• Access Episode 1 – Do you know your field heroes? Jennifer Otani (Agriculture and Agri-Food Canada-Beaverlodge) and Shaun Haney (RealAg). Published online May 12, 2020.

• Access Episode 2 – An inside look at the Prairie Pest Monitoring Network. Meghan Vankosky (Agriculture and Agri-Food Canada-Saskatoon) and Shaun Haney (RealAg). Published online May 26, 2020.

• Access Episode 3 – How much can one wasp save you? Haley Catton (Agriculture and Agri-Food Canada-Lethbridge) and Shaun Haney (RealAg). Published online June 9, 2020.

• Access Episode 4 – Eat and be eaten — grasshoppers as pests and food John Gavloski (Manitoba Agriculture and Resource Development) and Shaun Haney (RealAg). Published online June 23, 2020.

• Access Episode 5 – Killer wasp has only one target — wheat stem sawfly Scott Meers (Mayland Consulting) and Shaun Haney (RealAg). Published online July 7, 2020.

Access ALL the Field Heroes links here and be sure to follow @FieldHeroes!

West nile virus risk

Health 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 the most current weekly update (July 4, 2020). The screenshot below was retrieved 16Jul2020 as reference but access that information here.

This image has an empty alt attribute; its file name is 2020Jun28-Jul04_WNV_Weekly_HealthCanada-1024x593.png

The following is offered to predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies (Fig. 1). This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in the map below (yellow, orange then red highlighted areas). As of July 13, 2020, areas highlighted yellow and more imminently orange are approaching sufficient heat accumulation for mosquitoes to emerge. Plan to protect yourself by wearing DEET!

**Figure 1**. Predicted development of *Culex tarsalis*, across the Canadian prairies (as of July 13, 2020).

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 2020 are available. Access the July 1 5 , 2020 report. The summary indicates that, “Armyworms and grasshoppers continue to be the biggest insects concern on crops in Manitoba. Scouting for diamondback moth continues, with just one report of spraying for diamondback moth. Spraying for goosefoot groundling moth and a stem borer maggot has been reported from quinoa. Green cloverworm has been found on soybeans in eastern Manitoba, but not at levels that would be economical. Pupal clusters of Cotesia, a parasitoid of armyworms and other caterpillars, have been reported to be quite abundant in some of the fields that had armyworms.”

• Saskatchewan‘s Crop Production News and read Issue 5 which includes articles on Bertha armyworm, Cabbage seedpod weevil, FieldWatch – Fostering Communication Between Applicators and Producers, and Look What the Wind Blew in! Diamondback Moths Arrived Early This Spring. Issue #4 included articles on Pest Scouting 101: Mid-Summer, and The Wheat Midge.

• Alberta Agriculture and Forestry’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.