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TEMPERATURE: Average temperatures for the 2022 growing season have been similar to long term average values. This past week (August 1-7, 2022), the average daily temperature across the prairies was 2°C cooler than the previous week and 1°C warmer than the long-term normal (climate normal). The warmest temperatures were observed for the southern prairies (Fig. 1).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of August 1-7, 2022.
The prairie-wide average 30-day temperature (July 9 – August 7, 2022) was 1.5°C warmer than long-term average values. Average temperatures have been warmest across southeastern Alberta and southwestern Saskatchewan (Fig. 2).
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 9 to August 7, 2022.
The average growing season (April 1 – August 7, 2022) temperature for the prairies has been similar to that expected based on climate normal values. The growing season has been coolest across the Parkland and Peace River regions (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to August 7, 2022.
PRECIPITATION: The lowest weekly (August 1 to 7) precipitation accumulation occurred across southern and central regions of all three prairie provinces (Fig. 4). 30-day (July 9 – August 7, 2022) rainfall amounts have been well below average for northern and western Alberta and near normal across the central and southern regions of Alberta and Saskatchewan (Fig. 5). Precipitation has been above normal in southeastern Saskatchewan and eastern Manitoba.
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 1-7, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 9 to August 7, 2022).
Average growing season rainfall for the prairies (April 1 – August 7, 2022) has been approximately 160% of normal. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan. Cumulative rainfall amounts have been near normal for Saskatchewan and Alberta (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to August 7, 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 yet local development can vary and is only accurately assessed through in-field scouting.
Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.
Model simulations were used to estimate grasshopper development as of August 7, 2022. Potential risk continues to be greatest across central and southern regions of Saskatchewan and southeastern Alberta. Adults should now be occurring across central and southern regions of all three prairie provinces. Females are beginning to lay eggs in the soil. Development of grasshopper populations near Moose Jaw, Saskatchewan suggests that local populations are in the adult stage and that oviposition is progressing (Fig. 1). Model output indicates that populations are transitioning to the egg stage (Fig. 2). Potential risk continues to be greatest across the central and southern regions of Saskatchewan.
Figure 1. Predicted development of the migratory grasshopper (Melanoplus sanguinipes) population near Moose Jaw, Saskatchewan as of August 7, 2022.Figure 2. Percentage of the migratory grasshopper (Melanoplus sanguinipes) population expected to be in the egg stage across the Canadian prairies as of August 7, 2022.
Earlier oviposition can result in above average production of eggs and increased overwintering survival of eggs. The oviposition index provides a method to assess where egg production is greatest; higher oviposition index values indicate where egg production is greatest. Model runs for the 2022 growing season (April 1 to August 7, 2022) predict that oviposition rates should be greatest near Winnipeg, Manitoba, Moose Jaw, Saskatchewan and Medicine Hat, Alberta (Fig. 3).
Figure 3. Grasshopper (Melanoplus sanguinipes) oviposition index across the Canadian prairies as of August 7, 2022 . Higher ovipositional index values indicate greater potential for oviposition.
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 August 7, 2022, indicate that the third generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across most of the prairies (Fig. 1). DBM development is predicted to be marginally greater in 2022 than expected based on long-term 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 August 7, 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 August 7, 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 3. 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 4. Diamondback moth pupa within silken cocoon.
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 that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
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.
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 “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. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:
Remember your pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop. The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific. Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.
Here are a few resources to help: • Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website. • The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy. • Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate: ◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas. ◦ How long to wait, if the crop’s already been sprayed. ◦ To find a pesticide to suit your timeline. • Access the Pre-Harvest Glyphosate Stage Guide. • And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.
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.
