• Weather synopsis • Predicted grasshopper development • Predicted wheat midge development • Predicted diamondback development • Provincial entomologist updates • Links to crop reports • Review Insect of the Week for 2022 scouting help • Previous posts ….and Monday’s Insect of the Week for Week 9 – it’s the spotted lanternfly, Lycorma delicatula!
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.
TEMPERATURE: The 2022 growing season continues to be cooler while rainfall amounts have been highly variable across the prairies. This past week (June 27 – July 3, 2022) the average daily temperature (prairies) was 1 °C cooler than the previous week and 0.5 °C cooler than normal. The warmest temperatures were observed across the southern prairies (Fig. 1). The prairie-wide average 30-day temperature (June 4 – July 3, 2022) was 1 °C cooler than the long-term average value. Average temperatures have been warmest across the southern prairies, particularly for Saskatchewan and Manitoba (Fig. 2).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of June 27-July 3, 2022.Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 4-July 3, 2022.
The average growing season (April 1-July 3, 2022) temperature for the prairies has been 0.7 °C cooler than climate normal values. The growing season has been warmest across a region than extends from Lethbridge to Regina and Saskatoon (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 3, 2022.
PRECIPITATION: Weekly (June 27 – July 3) rainfall varied across the prairies. The highest rainfall amounts were reported for central Alberta and the Peace River region. Eastern Saskatchewan and Manitoba reported rainfall amounts that were generally less than 10 mm (Fig. 4). 30-day 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 June 27-July 3, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 4-July 3, 2022).
Growing season rainfall for April 1 – July 3, 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 3, 2022.
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.
Compared with the previous week, warm, dry conditions have advanced grasshopper development, particularly across central and southern regions of the prairies. Model simulations were used to estimate grasshopper development as of July 3, 2022. Based on estimates of average nymphal development, first to fifth instar nymphs should be occurring across southern and central regions of 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 3, 2022.Figure 2. Long-term average predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as the average instar, across the Canadian prairies as of July 3, based on climate normal data.
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 map in Figure 1 provides a visual representation of regional estimates of wheat midge movement to the soil surface, where pupal development will occur, then adults will begin to emerge. 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. Fields within regions receiving sufficient rainfall should scout! 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 3, 2022, model simulations predict that larvae (surface) and pupae are present with increased occurrence of adults. Larvae are completing development and transitioning to the pupal stage. Compared to last week, pupal populations are predicted to increase across the Parkland and Peace River regions (Fig. 1). Appearance of adults is predicted to increase across eastern Saskatchewan and southern Manitoba (Fig. 2). Occurrence of adults may be occurring when wheat is most susceptible. Occurrence of 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 10-12 days.
Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the pupal stage, across western Canada,as of July 3, 2022.Figure. 2. Percent of wheat midge population (Sitodiplosis mosellana) that is in the adult stage, across western Canada, as of July 3, 2022.Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewanas of July 3, 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. 4). 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 4. 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. 5), 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 5. 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!
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.
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.
Recent warm conditions should result in the development of DBM populations. Model simulations to July 3, 2022, indicate that the first generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the Canadian prairies and that the second generation is emerging across Manitoba and Saskatchewan (Fig. 1). DBM development is predicted to be similar to average values (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 3, 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 3, 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).
Figure 3. Diamondback moth pupa within silken cocoon.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access a PDF copy of the July 6, 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, barley thrips and blister beetles in MB were new additions to the July 6 issue. • Diamondback moth pheromone trap monitoring update for MB – Traps will come down at the end of this week. Review the detailed summary of cumulative trap counts from 52 sites deployed across the province (as of June 28, 2022). • 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.
ALBERTA’SInsect 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. • Diamondback moth pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map. • Cutworm live monitoring map for AB – Reports are mapped on this Live Map. Use this online form to report cutworms in Alberta.
The Insect of the Week features species you may encounter while scouting in field crops. This popular feature began with the release of the 2015 insect field guide and carries on today. Many thanks to all our contributors!
Need help finding information or a quick refresher when doing in-field scouting? Scroll the carousels to access the INSECT OF THE WEEK lineups for 2022 and the past 5 years:
