Welcome to Week 7 for the 2025 growing season! This week includes: • Weather synopsis • Predicted grasshopper development • Predicted bertha armyworm development • Diamondback moth • Wheat midge • Cabbage seedpod weevil • Lygus bug monitoring • Cereal leaf beetle • Monarch migration • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 7 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Fall armyworm!
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.
Dylan Sjolie, Tamara Rounce, Meghan Vankosky and Jennifer Otani
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Week 7
The seven-day average temperature across most of the Prairie growing region was above 14 °C last week (June 9 – June 15, 2025) (Fig.1). Southeastern Alberta and southwestern Saskatchewan experienced the warmest average temperatures between June 9 and June 15. Over the past 30 days, areas around Lethbridge and Swift Current have been the warmest, while areas surrounding Grand Prairie have been the coolest (Fig. 2). The far northern part of the prairie farming area, north of Grand Prairie in the Peace River region has also been quite warm in the last 30 days. Overall, the average temperature for the 2025 growing season (April 1 – June 15) is 9.5 °C, which is slightly above the long-term climate normal (Fig. 3).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for June 9-15, 2025.Figure 2. Thirty-day average temperature (°C) observed across the Canadian prairies for the period of May 17-June 15, 2025.Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-June 15, 2025.
Only a few areas north of Edmonton, Saskatoon, and Grand Prairie recorded more than 15 mm of rain between June 9-15, 2025 (Fig. 4). Cumulative rainfall amounts over the last 30 days are below 50 mm for much of the Prairie growing region (Fig. 5). Over the growing season, cumulative rainfall has been highest east of the Rocky Mountains in AB, and along the southern portion of the SK/MB border, which saw a significant rainfall event in May (cumulative rainfall between April 1 and June 15; Fig. 6).
Figure 4. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of June 9-15, 2025.Figure 5. Thirty-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 17-June 15, 2025.Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-June 15, 2025.
Dylan Sjolie, Tamara Rounce, Meghan Vankosky and Jennifer Otani
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Week 7
The grasshopper model was developed for the migratory grasshopper, but closely represents the development of the other primary pest grasshopper species found in the prairie region. The model uses weather from the current growing season to estimate the current status of grasshopper populations, but keep in mind that grasshoppers might not be present in all parts of the prairie region. Field scouting is imperative; the model estimates can be used to help time scouting activities.
The phenology model for grasshopper development on the prairies was developed by Olfert et al. (2021) and is described in: Olfert, O., R.M. Weiss, D. Giffen, M.A. Vankosky. 2021. Modelling ecological dynamics of a major agricultural pest insect (Melanoplus sanguinipes; Orthoptera: Acrididae): a cohort-based approach incorporating the effects of weather on grasshopper development and abundance. Journal of Economic Entomology 114: 122-130. DOI: 10.1093/jee/toaa254
Model simulations were used to estimate development of grasshoppers as of June 15, 2025,. The model outputs predict that grasshopper populations consist of mainly 2nd instar individuals (as of June 15, 2025), where grasshopper populations are present (Fig.1). These findings correspond with field observations from June 11th between Saskatoon and Rosetown, Saskatchewan. Based on the model readings, grasshopper development should be most advanced in areas surrounding Winnipeg, Manitoba, and in an area roughly located between Lethbridge, Alberta and Swift Current, Saskatchewan.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian Prairies as of June 15, 2025.
Dylan Sjolie, Tamara Rounce, John Gavloski, Meghan Vankosky and Jennifer Otani
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Week 7
The phenology model for bertha armyworm development on the Canadian prairies was developed by Ross Weiss and Owen Olfert. Model simulations were used to estimate development of bertha armyworm as of June 15, 2025.
The model indicates that in areas where bertha armyworm populations are present, the population should consist mainly of adults (Fig. 1). Based on the model readings, the percentage of adult berth armyworm in the population should be highest in Alberta and Saskatchewan. In some areas south of Winnipeg, east of Lethbridge, and northeast of Swift Current, the model predicts that female moths are already laying eggs (Fig. 2).
Figure 1. The proportion of the (Mamestra configurata) population that is predicted to be in the adult stage (% of total population) across the Canadian prairies as of June 15, 2025.Figure 2. The proportion of the (Mamestra configurata) population that is predicted to be in the egg stage (% of total population) across the Canadian prairies as of June 15, 2025.
Figure 3 includes photos of the various life stages of the bertha armyworm. There is one generation per year and pupae overwinter in the soil (Fig. 3, C). Each growing season, green unitraps utilizing pheromone lures are deployed and checked weekly over a 6-week window. Cumulative counts generated from the pheromone traps are used to estimate subsequent bertha armyworm densities. The cumulative moth count data is compiled using geospatial maps then posted to support and time in-field scouting for damaging populations of larvae by mid-July through to August.
Figure 3. Stages of bertha armyworm from egg (A), larva (B), pupa (C), to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
Please refer to this week’s Provincial Insect Pest Report Links to find the most up-to-date information summarizing weekly cumulative counts compiled by provincial pheromone trapping networks across the Canadian prairies in 2025. For example, Manitoba Agriculture’s June 19th Crop Pest Report includes Figure 4 with a reminder that other moth species are actively flying now so examine wing colourations and patterning carefully when checking the contents of bertha armyworm pheromone traps! Clover cutworm can be common by-catch in pheromone traps designed to monitor bertha armyworm, but also those designed to monitor true armyworm.
Figure 4. Comparison of diagnostic wing features of three moth species. Images and information all courtesy of Manitoba Agriculture, J. Gavloski who originally included in the June 19, 2025, issue of the Manitoba Crop Pest Update.
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” (2018), accessible as a free downloadable PDF in either English or French on our new Field Guides page. Also consider reviewing this 2019 Insect of the Week featuring bertha armyworm and its doppelganger, the clover cutworm!
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.
Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths (Fig. 1) attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.
Figure 1. Adult diamondback moth.
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.
Please refer to this week’s Provincial Insect Pest Report Links to find the most up-to-date information summarizing weekly cumulative counts compiled by provincial pheromone trapping networks across the Canadian prairies in 2025.
Dylan Sjolie, Tamara Rounce, Meghan Vankosky and Jennifer Otani
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Week 7
The emergence of adult wheat midge (Sitodiplosis mosellana) needs to be synchronized with the development of wheat heads for successful larval development. One factor that determines the timing of adult wheat midge emergence is spring precipitation. Cumulative rainfall between 25-30 mm in May and June is required for overwintered larval cocoons to complete larval and pupal development in the spring. When cumulative rainfall is below 25-30 mm in May and June, the completion of larval development may be delayed or postponed to future growing seasons, resulting in delayed or erratic adult wheat midge emergence in late June and July.
Cumulative rain (May 1-June 15) across the majority of Alberta and Manitoba now exceeds the threshold (30 mm) required to terminate larval diapause (Fig. 1). Several areas including surrounding Saskatoon (Rosetown, North Battleford, Elbow) and west of Lethbridge (Medicine Hat, Maple Creek, Alsask) have not reached this threshold. However, this is likely to change if those areas receive 10 mm or more of rainfall over the next week.
Figure 1. Areas in western Canada where cumulative rainfall from May 1 to June 15, 2025 is equal to or greater than 30 mm, which is the threshold required to promote movement of wheat midge (Sitodiplosis mosellana) larvae to the soil surface where they will pupate.
Based on model readings, where wheat midge populations are present, larvae have begun to move to the soil surface (Fig. 2). Where wheat midge populations exist, the proportion of the larval population at the soil surface and ready to pupate is highest in eastern AB, southeastern SK, and southwestern MB. Model output suggests that pupation should start to occur next week.
Figure 2. Percent of wheat midge larval population (Sitodiplosis mosellana) that has moved to the soil surface across western Canada, as of June 15, 2025.
Please refer to the historical wheat midge survey maps and particularly the 2024 results. Historical survey information paired with updated predictive model outputs help identify areas at risk of wheat midge damage in 2025.
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. 3). 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 3. Wheat midge (Sitodiplosis mosellana) laying their eggs on a wheat head. Photo: AAFC-Beav-S. Dufton and A. Jorgensen.Figure 4. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long. Photo: AAFC-Beav-S. Dufton.
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. 4), 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.
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 2023 (for Wk08). 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 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.
There is one generation of cabbage seedpod weevil (CSPW; Ceutorhynchus obstrictus) per year. The overwintered adult is an ash-grey weevil measuring 3-4mm long (Fig. 1; left photo). Mating and oviposition are quickly followed by eggs hatching within developing canola pods (Fig. 1; right photo). The highly concealed larvae feed within the pod, consuming the developing seeds.
Figure 1. Cabbage seedpod weevil (left) and egg dissected from within a canola pod (right). Photos: the late Dr. Lloyd Dosdall.
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 (Fig. 1; 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 (Fig. 2; 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 (Fig. 2; right photo, lower pod), feeding on the developing seeds. A single larva consumes about 5 canola seeds. The mature larva chews a small, circular exit hole (Fig. 2; right photo, upper pod) 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.
Figure 2. Larva feeding amongst developing seeds within canola pod (left) and larval entrance hole (right photo, lower pod) compared to mature larval exit hole (right photo, uppower pod). Photos: the late Dr. Lloyd Dosdall.
Prairie-Wide Monitoring: The annual cabbage seedpod weevil survey is performed in canola at early flower stages using sweep-net collections. Review the prairie-wide historical survey maps for this insect species. Review the PPMN monitoring protocol although the provinces of Alberta, Saskatchewan, and Manitoba have specific survey protocols for their respective network cooperators. Commercial fields where comparatively higher densities of adult cabbage seedpod weevils were observed in 2024 are highlighted yellow, orange, or red in the geospatial map featured in Figure 3.Areas where historically higher densities of cabbage seedpod weevil were observed in 2024 are worth prioritizing in 2025.
Figure 3. Densities of cabbage seedpod weevil (Ceutorhynchus obstrictus) observed in sweep-net samples retrieved from commercial fields of canola (Brassica napus) grown in Manitoba, Saskatchewan, Alberta, and the British Columbia portion of the Peace River region in 2024.
In-Field 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.
Albertan growers can report field observations and check the live map for CSPW posted by Alberta Agriculture and Irrigation (screenshot provided below as an example; retrieved 2025Jun19 but will be updated with 2025 reports as the season progresses).
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 continues 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.
The cereal leaf beetle (Chrysomelidae: Oulema melanopus) has a broad host range. Wheat is the preferred host, but adults and larvae also feed on leaf tissue of oats, barley, corn, rye, triticale, reed canarygrass, ryegrass, fescue, wild oats, millet and other grasses. Yield quality and quantity is decreased, if the flag leaf is stripped. Fun fact: Cereal leaf beetle larvae carry their own fecal waste above their body to help protect themselves from predators.
Fortunately, the parasitoid wasp, Tetrastichus julis Walker (Hymenoptera: Eulophidae), is an important natural enemy of cereal leaf beetle larvae. Learn more about this beneficial insect species featured in Week 9 of 2023’s Insect of the Week!
Cereal Leaf Beetle Lifecycle and Damage:
Adult: Adult cereal leaf beetles (CLB) have shiny bluish-black wing covers (Fig. 1). The thorax and legs are light orange-brown. Females (4.9 to 5.5 mm) are slightly larger than males (4.4 to 5 mm). Adult beetles overwinter in and along the margins of grain fields in protected places such as in straw stubble, under crop and leaf litter, and in the crevices of tree bark. They favour sites adjacent to shelterbelts, deciduous and conifer forests. They emerge in the spring once temperatures reach 10-15 ºC and the adults are active for about 6 weeks. They usually begin feeding on grasses, then move into winter cereals and later into spring cereals.
Figure 1. Adult Oulema melanopus measure 4.4-5.5 mm long (Photo: M. Dolinski).
Egg: Eggs are laid approximately 14 days following the emergence of the adults. Eggs are laid singly or in pairs along the midvein on the upper side of the leaf and are cylindrical, measuring 0.9 mm by 0.4 mm, and yellowish in colour. Eggs darken to black just before hatching.
Larva: The larvae hatch 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. 2). When the larva completes its growth, it drops to the ground and pupates in the soil.
Figure 2. Larval stage of Oulema melanopus with characteristic feeding damage visible on leaf (Photo: M. Dolinski).
Pupa: Pupal colour varies from a bright yellow when it is first formed, to the colour of the adult just before emergence. 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.
Access scouting tips for cereal leaf beetle or find more detailed information by accessing the Oulema melanopus page from 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.
Track the migration of the Monarch butterflies as they move north by checking the 2025 Monarch Migration Map! A screenshot of Journey North’s “first sightings of adults” map is below (retrieved 2025Jun19) but follow the hyperlink to check the interactive map.
Jennifer Otani, John Gavloski, James Tansey, Carter Peru, Amanda Jorgensen and Shelley Barkley
Categories
Week 7
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to access their information as the growing season progresses:
MANITOBA’SCrop Pest Updates for 2025 have started! Review a PDF copy of the latest reports released June 12, 2025 and June 19, 2025! • Insect pests named in the June 12th report include cutworms, wireworms, seedcorn maggot, flea beetles, and pea leaf weevil. • Insect pests named in the June 19th report include alfalfa weevil, flea beetles, cutworms, wireworms, wireworms, and black flies. An extremely helpful set of images of by-catch and bertha armyworm moths is included in this report! • Cumulative 2025 counts of intercepted diamondback moths are updated weekly to provide regional information to producers and guide in-field scouting. • Pheromone-baited trap counts are available for true armyworms in these reports plus the most recent issue includes tips to identify the larvae. • Bookmark the Crop Pest Update Index and the insect pest homepage to access fact sheets and more!
SASKATCHEWAN’SCrop Production News is coming soon. Bookmark their insect pest homepage to access important information! Access and review theCrops Blog Posts. Thanks to J. Tansey with Saskatchewan Agriculture for sharing the following update (as of June 19, 2025): •Bertha armyworm moths are being intercepted at sites in SK. Stay tuned for updates as more data comes in over the coming weeks.
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. Remember AAF’s Agri-News includes insect-related information: • June 16, 2025, issue includes links to how to submit reports for cabbage seedpod weevil and access the live map. plus links to the live diamondback moth and bertha armyworm maps – be sure to refresh to upload the latest information! • Diamondback moth pheromone trap live monitoring map for AB – Cumulative counts derived from weekly data are now being generated so refer to the Live map. • Bertha armyworm pheromone trap live monitoring map for AB – Cumulative counts derived from weekly data will be generated so refer to the Live map. • Cabbage seedpod weevil live sweep-net monitoring map for AB – In-field reports are uploaded daily so refer to the Live map.
