Welcome to Week 8 for the 2025 growing season! This week includes: • Weather synopsis • Predicted grasshopper development • Predicted wheat midge development • Cereal leaf beetle • Wheat head armyworm • Aphids in field crops • Lygus bug monitoring • Cabbage seedpod weevil • Predicted diamondback moth development • Predicted bertha armyworm development • European skipper • Monarch migration • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 8 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Spotted wing drosophila!
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.
The seven-day average temperature across the Canadian prairies was slightly above 14 °C from June 16-22, 2025 (Fig. 1). Areas surrounding Winnipeg and Brandon received the warmest average temperatures, while areas around Calgary and Grand Prairie experienced the coolest temperatures. Over the past 30 days, the average temperature across the Canadian prairies was around 15 °C (Fig. 2), which is slightly above the long-term climate normal. Since April 1, 2025, production areas near Lethbridge AB and Winnipeg MB have been the warmest, whereas areas near Grande Prairie AB have been the coolest (Fig. 3).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for June 16-22, 2025.Figure 2. Thirty-day average temperature (°C) observed across the Canadian prairies for the period of May 24-June 22, 2025.Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-June 22, 2025.
The average cumulative rainfall amounts over the last seven days across the Canadian prairies was 25 mm (Fig. 4; June 16 – June 22). Locally, higher rainfall was reported in areas surrounding Calgary and Lethbridge in Alberta plus Kindersley and Rosetown in Saskatchewan; between 70 – 100 mm of rain fell in those areas (Fig. 4). Outside of the areas receiving significant rainfall events in the last 7 days, the cumulative 30-day rainfall remains less than 70 mm for most of western Canada (Fig. 5). Over the growing season (April 1-June 22, 2025), areas surrounding Lethbridge and Calgary AB have received >200 mm of cumulative rainfall, whereas much of Saskatchewan, Manitoba, and the Peace River region have received <100 mm (Fig. 6).
Figure 4. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of June 16-22, 2025.Figure 5. Thirty-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 24-June 22, 2025.Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-June 22, 2025.
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 the development of grasshoppers as of June 22, 2025. The model outputs predict that grasshopper populations, where present, consist mainly of 2nd and 3rd instar nymphs (Fig. 1). These findings correspond with field observations between Saskatoon and Rosetown, Saskatchewan, on June 20, 2025. Based on the model readings, grasshopper development should be most advanced in areas surrounding Winnipeg in Manitoba, and east of Lethbridge in Alberta.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian Prairies as of June 22, 2025.
The emergence of 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 rainfall (May 1-June 22, 2025) across the majority of Prairie growing region now exceeds the threshold (30 mm) required to terminate larval diapause.
The model indicates that, where wheat midge populations are present, larvae continue to move to the soil surface (Fig. 1). Although areas surrounding Saskatoon and Swift Current in Saskatchewan and west of Lethbridge in Alberta show low larval populations at the soil surface, this is likely to change as those areas have now received sufficient rainfall over the past week to trigger emergence from larval cocoons (June 16 – June 22). Model output suggests that pupae should be present in the southwest corner of Saskatchewan, in areas between Edmonton and Calgary in Alberta, and around Brandon in Manitoba (Fig. 2).
Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that has moved to the soil surface across western Canada, as of June 22, 2025.Figure 2. Percent of wheat midge larval population (Sitodiplosis mosellana) that has moved to the soil surface across western Canada, as of June 22, 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.
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.
Wheat head armyworm (Lepidoptera: Noctuidae): Dargida diffusa (Walker, 1856) feeds on several grassy-type species including wheat, rye, oats, barley, wild oats, native and forage grasses (although timothy is preferred). Wheat head armyworm overwinter within earthen cells as pupae. Each growing season, there are two generations of adults produced. This means both a spring and summer larval generation occur, however, the first generation can cause damage early in the growing season in wheat and some grasses (Fig. 1) although infestations are very sporadic and rarely reach densities requiring control.
Figure 1. Wheat head armyworm larva (Noctuidae: Dargida diffusa) and frass (larval poop) plus shed larval head capsule where developing kernel formed but was consumed. Photo kindly shared by: B. DeSmet, Dirt Road Agronomy.
Adult moths are 30-38 mm in wing span, are yellowish-brown, but have a chocolate-brown stripe running down the length of each forewing. Larvae have a pale brown head capsule, grow to ~25 mm long, and are bright green or tan with lateral white stripes that help camouflage them on awns (Fig. 2). The previous alternate scientific name for this species was Faronta diffusa. Wheat head armyworm are surprisingly difficult to spot in situ and are sometimes initially detected in sweep-nets (Fig. 3).
Figure 2. Examples of three colour morphs of wheat head armyworm (Noctuidae: Dargida diffusa) on cereals growing in the Peace River region in 2024; note consistent stripe patterning but larval body colour can range from bright green to tan. Photos kindly shared by: B. DeSmet, Dirt Road Agronomy.Figure 3. Green and tan colour morphs of wheat head armyworm (Noctuidae: Dargida diffusa) retrieved in sweep-net sample on August 10, 2020, in wheat growing near Magrath AB. Photo kindly shared by: A. Voss, @Voss_Ag
Infestations are very sporadic. There is no nominal or economic threshold for this species in any of the field crop species listed above. Beneficial insects like the parasitoid wasps within the genus Cotesia will attack wheat head armyworm larvae and, shortly after erupting from the larval host, will form clusters of white cocoons (Fig. 4) that eventually yield new parasitoid wasps which subsequently seek out and attack other armyworms.
Figure 4. Cotesia cocoons spun on wheat awns that presumably erupted from immobile larva of wheat head armyworm (Noctuidae: Dargida diffusa) that has numerous lateral exit wounds. Photo taken August 10, 2020, near Magrath AB and kindly shared by:A. Voss, @Voss_Ag
Distribution records for D. diffusa can be reviewed on the Butterflies of North America website although these records would greatly benefit with sightings in western Canada because the species is established in Alberta (central and in the south east of the Peace River region), in Saskatchewan, and Manitoba.
Biological and monitoring information for this insect pest species is accessible as a wheat head armyworm page within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018). The entire guide is accessible as a free downloadable PDF in either English or French on our Field Guides page.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Access the Provincial Insect Pest Report for Wk15 to remain alert to areas and crops suffering from aphid pest pressure.
Figure 1. Pea aphid adults (each 3-4 mm long) and nymph. Photo: M. Dolinski.
Additionally, several aphid pest species are described in the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) which is accessible as a free downloadable PDF in either English or French on our Field Guides page. PDF copies of the individual pages have been linked below to access quickly: • Corn leaf aphid or Rhopalosiphum maidis (Fitch) • English grain aphid or Sitobion (Macrosiphum) avenae (Fabricius) • Oat-birdcherry aphid or Rhopalosiphum padi (Linnaeus) • Pea aphid or Acyrthosiphon pisum (Harris) • Potato aphid or Macrosiphum euphorbiae (Thomas) • Soybean aphid or Aphis glycines (Matsumura) • Turnip aphid or Lipaphis erysimi (Kaltenbach) • Sugar beet root aphid or Pemphigus betae Doane • Russian wheat aphid or Diuraphis noxia (Mordvilko)
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.
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).
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.
Diamondback moths were captured on pheromone traps across western Canada from mid- to late-May in 2025. Once adults arrive, there can be several in-season, non-migrant generations of diamondback moth developing throughout the remainder of the growing season. Warm, dry weather tends to promote rapid development of high-density populations of larvae capable of causing severe damage to host crops, including canola.
As of June 22, 2025, model outputs predict that diamondback moth populations are in the first non-migrant generation (Fig. 2).
Figure 2. Predicted number of in-season generations of diamondback moth (Plutella xylostella) expected to have developed across the Canadian prairies, as of June 22, 2025.
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.
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. 3) 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.
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 22, 2025.
The model outputs predict that bertha armyworm populations, where present, should consist mainly of adults laying eggs (Fig. 1). Based on the model outputs, populations throughout most of Alberta and Saskatchewan are predicted to be mainly be in the egg stage (as of June 22, 2025). In some areas south of Winnipeg, east of Lethbridge, and northeast of Swift Current, larvae may be present (Fig. 2).
Figure 1. 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 22, 2025.Figure 2. The proportion of the (Mamestra configurata) population that is predicted to be in the LARVAL stage (% of total population) across the Canadian prairies as of June 22, 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 Field Guides page. Also consider reviewing this 2019 Insect of the Week featuring bertha armyworm and its doppelganger, the clover cutworm!
The European skipper (Hesperiidae: Thymelicus lineola) is a diurnal, bright orange butterfly (Fig. 1). The predominantly green defoliating larvae can cause economic levels of damage in timothy. The larvae also feed on other species of grasses and winter wheat.
Figure 1. European skipper (Thymelicus lineola) adults on timothy seed seeds. 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. Host plants include timothy (Phleum pretense), cocksfoot (Dactylis glomerata), couch or quack grass (Agrophyron repens), perennial ryegrass (Lolium perenne), meadow fescue (Festuca pratensis), orchardgrass (Dactylis glomerata).
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. Eggs can be transferred in both hay and seed as seed cleaning will not remove all eggs. Early the following 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.
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 behaviour 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 the larva remains 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.
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. Nectar sources for adults include orange hawkweed, thistles, oxeye daisy, fleabane, white clover, red clover, common milkweed.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.
Access the Provincial Insect Pest Report for Wk09 for updates for this economic insect pest.
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 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).Figure 5. In situ camouflaged larvae and feeding damage in timothy. Photo: S. Barkley.
The European skipper was introduced to North America at least a century 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.
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.).
The European skipper was the Insect of the Week in 2022 (Wk10).
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 (Fig. 1; retrieved 2025Jun25) but follow the hyperlink to check the interactive map.
We also share a screenshot of Journey North’s “first sightings of LARVAE” map is below (Fig. 2; retrieved 2025Jun25).
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 26, 2025! • Insect pests named in the June 26th report include true armyworm, alfalfa weevil, thrips, and cereal leaf beetle. The cabbage seedpod weevil survey is set to begin and targets canola fields as they start to flower. • 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. • Cumulative 2025 counts of intercepted bertha armyworm moths are updated weekly. • Bookmark the Crop Pest Update Index and the insect pest homepage to access fact sheets and more!
SASKATCHEWAN’SInsect pest homepage links to important information! Thanks to J. Tansey with Saskatchewan Agriculture for sharing the following update (as of June 26, 2025): • Peritrechus convivus damage has been reported in canola, and durum. There are no thresholds and no registered control products. Please report populations to Tyler.Wist@agr.gc.ca or James.Tansey@gov.sk.ca Adults are brownish-black seed bugs (link to iNaturalist.ca for images of adults) but nymphs are typically aggregated, have a vividly red abdomen with blackish-brown head and thorax (link to 2022 The Western Producer article for image of nymph). • Substantial rain should bring relief to wheat crops affected by brown wheat mite. • Flea beetle populations are waning as the canola crop develops. • Significant cabbage seedpod weevil populations have been reported in the SW and Central regions • Large numbers of pea aphid have been reported in alfalfa hay with the first cut in several regions of SK. There were reports of poor performance of lambda-cyhalothrin insecticides in pea aphid populations in 2024. In response, we have prepared field test kits to assess sensitivity of pea aphid to the insecticide lambda-cyhalothrin but test kit numbers are limited.
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 23, 2025, issue notes that the 2025 cabbage seedpod weevil survey has started in southern Alberta, containtes links to the CSPW reporting tool, and 2024 survey results. It also notes a report of red turnip beetles in canola. • 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. • Wheat midge live sweep-net monitoring map for AB – Cumulative counts derived from weekly data will be generated so refer to the Live map.
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.
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.
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.
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.
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.
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.
Welcome to Week 6 for the 2025 growing season! This week includes: • Weather synopsis • Predicted grasshopper development • Predicted bertha armyworm development • Wireworms • Alfalfa weevil • Cereal leaf beetle • Cabbage seedpod weevil • Diamondback moth • Monarch migration • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 6 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Soybean gall midge!
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.
Similar to last week, the majority of the Prairie growing region was very warm between June 02 and June 08, with areas recording average temperatures around 13 °C (Fig. 1). In late May and early June, areas surrounding Winnipeg and Lethbridge were the warmest, whereas Grande Prairie was the coolest (Fig. 2). Overall, growing season average temperatures have been above 9 °C for much of the Prairies with lower temperatures recorded in northern Alberta and the northern border of Manitoba and Saskatchewan (Fig. 3).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for June 2-8, 2025.Figure 2. Thirty-day average temperature (°C) observed across the Canadian prairies for the period of May 10-June 8, 2025.Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-June 8, 2025.
Some much-needed rain fell in areas east of Saskatoon and south of Lethbridge last week, but other regions recorded very little rainfall (Fig. 4). In the entire month of May, rainfall was highest along the Rocky Mountains in Alberta and the southeast corner of Saskatchewan, in the Estevan area (Fig. 5). Over the growing season so far (April 1 – June 08), large areas in Prairie growing region have yet to receive more than 100 mm of cumulative rainfall (Fig. 6).
Figure 4. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of June 2-8, 2025.Figure 5. Thirty-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 10-June 8, 2025.Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-June 8, 2025.
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 8, 2025. Based on model outputs, the average hatch percentage is just over 50 % (Fig. 1). Hatch is predicted to be highest around Winnipeg and between Lethbridge and Saskatoon.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) hatch (%) across the Canadian Prairies as of June 8, 2025.
As of June 8, 2025, grasshopper populations, where present, are predicted to consist of mainly 1st or 2nd instar individuals (Fig. 2). These findings correspond with field observations from June 5th between Saskatoon and Rosetown. Based on the model readings, grasshopper development is predicted to be most advanced in areas surrounding Winnipeg and Brandon in Manitoba, Swift Current in Saskatchewan, and east of Lethbridge in Alberta.
Figure 2. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian Prairies as of June 8, 2025.
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 8, 2025. Model outputs predict that the adult flight has likely started in most areas where bertha armyworm populations are present except for in parts of the BC Peace River region and along the foothills in western Alberta where the percentage of the population in the adult stage is estimated to be less than 15 % (Fig. 1). Based on the model readings, the percentage of bertha armyworm in the adult stage, where populations are present, should be highest in areas between Edmonton and Calgary in Alberta.
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 8, 2025.
Figure 2 includes photos of the various life stages of the bertha armyworm. There is one generation per year and pupae overwinter in the soil (Fig. 2, 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 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C), to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
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 the 2019 Insect of the Week, which featured bertha armyworm and its doppelganger, the clover cutworm!
Reminder – Wireworms are the larval stage of click beetles from the family Elateridae. Click beetles, the adult stage, do not cause damage to crops. Wireworms live in the soil, where it can take 4 or more years to complete larval development. In the soil, wireworms feed on germinating seeds and the roots of a wide variety of prairie field crops including cereals, pulses, oilseeds, and vegetables including potato and carrots. Damage to root vegetables can result in unmarketable produce.
Several species of wireworms can be found on the Canadian Prairies but species commonly occurring in field crops are included in Figure 1. Even more importantly, there are four primary pest species, including Hypnoidus bicolor, prairie grain wireworm (Selatosomus aeripennis destructor), sugarbeet wireworm (Limonius californicus), and flat wireworm (Aeolus mellillus).
Figure 1. Dorsal views of economically important species of wireworms observed across the Canadian prairies and their adult click beetle. (Source: Guide to Pest Wireworms in Canadian Prairie Field Crop Production).
Similar to cutworms, bare patches in a field can be an early and obvious sign of wireworm infestation in the spring. Patchy crop emergence (Fig. 2), results when wireworms consume germinating seeds or feed on the roots and stems of young seedlings (Fig. 3).
Figure 2. A cereal field with patchy seedling emergence and stand establishment due to wireworm infestation. Picture by Dr. Haley Catton (AAFC, Lethbridge).Figure 3. Wireworm feeding damage on a faba bean seedling. Picture by Chris Baan.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 1). The green larva features a dorsal white line down the length of its body, has a dark brown head capsule, and will grow to 9 mm long.
Figure 1. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
Alfalfa growers are encouraged to check an updatedProtocol for Monitoring Alfalfa Weevil prepared by Guelly et al. 2025. 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” (2018; accessible in either English-enhanced or French-enhanced versions)
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.
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 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 2022Jul28 but will be updated with 2025 reports as season progresses).
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.
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 2025Jun11) but follow the hyperlink to check the interactive map.
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 report released June 5, 2025. • Insect pests named in this report include cutworms, flea beetles, pea leaf weevil, diamondback moth, true armyworms, and soldier beetles. • Cumulative 2025 counts of intercepted diamondback moths are updated and posted weekly on Thursdays (or as soon as available) to provide regional information to producers and guide in-field scouting. • Pheromone-baited trap counts are also available for true armyworms in this report. • 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 10, 2025): •Significant flea beetle damage and reseeding reported near Melfort and Maymont. Crucifer flea beetle was indicated as the dominant species near Maymont. •Brown wheat mite reported as damaging on durum near Kimberley. •Significant damage from brown stinkbug (Euchistus) in alfalfa hay near Esterhazy. •Red bug (Peritrechus convivus) damage reported in seedling alfalfa near Cupar. •Grasshopper hatch reported as ongoing in several regions with moderate numbers noted near Kindersley. Nymphs appear to be limited to ditches currently. •Diamondback moth interception counts remain low to moderate in most regions, although numbers are increasing. •Significant pea leaf weevil damage was detected on a few sites in the Southeast and West Central regions of the province while populations are low to moderate in the Northeast regions. The annual survey is nearly completed.
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 9, 2025 issue includes an insect update noting presence and advancing development of pest grasshopper species, continued need for flea beetle monitoring in seedling canola, links to the diamondback moth live map and cutworm live map. Additionally, annual pea leaf weevil monitoring will wrap up soon and a reminder to consider field heroes, if tank mixes are being considered that involve inclusion of a registered insecticide. • June 2, 2025 issue includes how to assess flea beetle risk, links to the cutworm live map and diamondback moth live map, plus notification that bertha armyworm traps will be deployed the week of June 8. • 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 which will start to update as of June 15.
Welcome to Week 5 for the 2025 growing season! This week includes: • Weather synopsis • Wireworms • Predicted grasshopper development • Grasshopper diversity and scouting • Cereal leaf beetle • Pea leaf weevil • Alfalfa weevil • Cabbage seedpod weevil • Diamondback moth • Bertha armyworm • Active wildfires and air quality • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 5 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Swede midge!
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.
The majority of the Prairie region was very warm last week (May 26 – June 01, 2025) with most areas recording average temperatures above 17 °C (Fig. 1). Temperatures were slightly cooler in northern Alberta around Grand Prairie. Growing season average temperatures have been highest in southern Alberta and Saskatchewan, and lowest in northern Alberta and the northern border of Manitoba and Saskatchewan (Fig. 2).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for May 26-June 1, 2025.Figure 2. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-June 1, 2025.
Much of the Prairies went without rainfall between May 26 and June 01, except in areas north of Edmonton (Athabasca and Lesser Slave River counties) (Fig. 3). Overall, large areas in prairie growing region have received less than 100 mm of cumulative rainfall this growing season (cumulative rainfall between April 1 and June 01; Fig. 4).
Figure 3. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of May 26-June 1, 2025.Figure 4. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-June 1, 2025.
Reminder – Wireworms are the larval stage of click beetles from the family Elateridae. Click beetles, the adult stage, do not cause damage to crops. Wireworms live in the soil, where it can take 4 or more years to complete larval development. In the soil, wireworms feed on germinating seeds and the roots of a wide variety of prairie field crops including cereals, pulses, oilseeds, and vegetables including potato and carrots. Damage to root vegetables can result in unmarketable produce.
Several species of wireworms can be found on the Canadian Prairies but species commonly occurring in field crops are included in Figure 1. Even more importantly, there are four primary pest species, including Hypnoidus bicolor, prairie grain wireworm (Selatosomus aeripennis destructor), sugarbeet wireworm (Limonius californicus), and flat wireworm (Aeolus mellillus).
Figure 1. Dorsal views of economically important species of wireworms observed across the Canadian prairies and their adult click beetle. (Source: Guide to Pest Wireworms in Canadian Prairie Field Crop Production).
Similar to cutworms, bare patches in a field can be an early and obvious sign of wireworm infestation in the spring. Patchy crop emergence (Fig. 2), results when wireworms consume germinating seeds or feed on the roots and stems of young seedlings (Fig. 3).
Figure 2. A cereal field with patchy seedling emergence and stand establishment due to wireworm infestation. Picture by Dr. Haley Catton (AAFC, Lethbridge).Figure 3. Wireworm feeding damage on a faba bean seedling. Picture by Chris Baan.
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 01, 2025. As temperatures begin to increase, the rate of grasshopper development is also beginning to increase across the Prairie region. Based on model outputs, the average hatch percentage is about 30% (Fig. 1). Hatch is predicted to be highest around Winnipeg, Swift Current, and east of Lethbridge.
Figure 1. Predicted grasshopper (Melanoplus sanguinipes) hatch (%) across the Canadian Prairies as of June 1, 2025.
As of June 01, 2025, grasshopper populations, where present are predicted to consist of mainly first instar individuals (Fig. 2). These findings correspond with field observations from May 30 between Saskatoon and Rosetown. Based on the model readings, grasshopper development should be most advanced around Brandon and east of Winnipeg in Manitoba and in an area extending roughly from Medicine Hat to Swift Current in Alberta and Saskatchewan.
Figure 2. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian Prairies as of June 01, 2025.
Prairie-Wide Monitoring: Annual grasshopper surveying is performed across western Canada by visually estimating densities in late summer. 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 pest species of grasshoppers were observed in 2024 are highlighted yellow, orange, or red in the geospatial map featured in Figure 1. Areas where historically higher densities of grasshoppers were observed in 2024 are worth prioritizing in 2025.
Figure 1. Densities of grasshoppers observed by visual in-field observations in late summer of 2024.
Grasshopper Scouting Tips: ● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species (Gavloski, Williams, Underwood, Johnson, Otani) to aid with field scouting from egg hatch and onwards. The PDF includes photos to help differentiate native versus pest grasshopper species plus froghopper, treehopper or even katydid species. ● It is best to scout on warm days when grasshopper nymphs are more active and easier to observe. ● Carefully check roadside ditches and along field edges but also check the edge of the crop and into the actual field. ● Younger or earlier instar nymphs are easier to manage – visit sites every few days to stay on top of local field conditions. ● A sweep-net can ‘detect’ grasshopper nymphs, however, economic thresholds for grasshoppers are based on the number of grasshoppers per square-metre counts. ● 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.
Important – A preliminary summary of available thresholds for grasshoppers has been kindly shared by Dr. J. Tansey (Saskatchewan Agriculture) in Table 1. When scouting, compare in-field counts to the available threshold value for the appropriate host crop AND for field or ditch situations. Available thresholds (nominal and economic) help support producers while protecting beneficials (i.e., predators, parasitoids, and pathogens) that regulate natural populations of grasshoppers.
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.
The annual pea leaf weevil survey is underway! The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge (Fig. 1).
Figure 1. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent-shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches. All photos courtesy of Dr. L. Dosdall.
In the spring, overwintered adults disperse to feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas). This feeding can produce a characteristic, scalloped (or notched) edges (Fig. 2). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Adult pea leaf weevil feeding and creating characteristic “notch” at edge of faba bean leaf. Photo: AAFC-Saskatoon-Williams.
The annual pea leaf weevil survey is conducted from late May to early June. The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge. Review the prairie-wide historical survey maps. Higher levels of feeding damage are correlated to higher pea leaf weevil densities so areas highlighted in Figure 3 warrant in-field monitoring in the spring of 2025.
Figure 3. Results of the annual pea leaf weevil survey conducted in the spring of 2024.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol. Access the Pea leaf weevil information posted by the Manitoba Pulse & Soybean Growers, Saskatchewan Agriculture, Alberta Agriculture and Irrigation, or the Prairie Pest Monitoring Network. Also refer to the pea leaf weevil page 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 Field Guides page.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 1). The green larva features a dorsal white line down the length of its body, has a dark brown head capsule, and will grow to 9 mm long.
Figure 1. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
Alfalfa growers are encouraged to check an updatedProtocol for Monitoring Alfalfa Weevil prepared by Guelly et al. 2025. 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” (2018; accessible in either English-enhanced or French-enhanced versions).
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 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 2022Jul28 but will be updated with 2025 reports as season progresses).
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.
Degree-days can be used to predict the timing of insect development and plan for pest scouting and management. Degree-days are calculated for different insect species using temperature thresholds specific to their development. Based on research, the temperature threshold for bertha armyworm (Mamestra configurata) development is 7 °C and 352 accumulated degree-days (base 7 °C) are required for overwintered pupae to begin their spring development phase. As of May 25, there are no areas on the prairies that have surpassed the degree-day requirement for pupal development of bertha armyworm (Fig. 1).
Figure 1. Growing degree-day heat units (Base 7 °C) accumulated across the Canadian prairies from April 1 to May 25, 2025.
Pheromone traps used to monitor bertha armyworm are typically set up along canola fields when pupal development reaches 75-80%; the 2024 monitoring season started the week of June 10, 2024. Cumulative counts from sentinel pheromone monitoring sites targeting bertha armyworm moths across the Canadian prairies in 2024 are highlighted as geospatial areas where producers are encouraged to prioritize in-field monitoring in 2025. Areas in Figure 2 highlighted yellow, orange, or especially red hosted pheromone traps that intercepted relatively high cumulative counts of moths in 2024 and should be prioritized for in-field scouting in 2025. Review the prairie-wide historical survey maps for this insect species.
Figure 2. Cumulative weekly counts of Bertha armyworm (Mamestra configurata) moths arising from the 2024 growing season.
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. Cumlative 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).
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 the 2019 Insect of the Week, which featured bertha armyworm and its doppelganger, the clover cutworm!
Active Wildfires – Natural Resources Canada’s Canadian Wildland Fire Information System (CWFIS) creates and updates daily fire weather and fire behaviour maps year-round with hot spot maps updated daily between May and September. The website features three types of maps plus valuable links. Maps to access include: • Fire Weather • Fire Behaviour • Fire M3 Hotspotand example of the map for June 4, 2025, is copied below (Fig. 1).
Persons outdoors performing field scouting need to be aware of air quality arising from wildfire activity. Two online resources are available – both are updated daily and provide short video clips of forecasted ground level smoke conditions: • FireSmoke.ca (Figure 2 for example). • Firework (Figure 3 for example).
Figure 2. Snip of smoke forecast retrieved June 5, 2025 at 15:05 from FireSmoke.ca predicting for June 6, 2025 at 11:00 UTC.Figure 3. Snip of smoke forecast retrieved June 5, 2025, at 15:06 from CWFIS’s Firework (Fine Particulate Matter webpage forecasting for Jun 6, 2025 at 9:00 MDT.
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to access their information as the growing season progresses:
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 2, 2025 issue includes how to assess flea beetle risk, links to the cutworm live map and diamondback moth live map, plus notification that bertha armyworm traps will be deployed the week of June 8 and that the live map will begin updating June 15. • May 26, 2025 issue includes notification that pea leaf weevil survey has begun, continued flea beetle pressure and need to monitor seedling canola plus mustard, continuation of cutworm monitoring (and link to live cutworm map). • Cutworm live monitoring map for AB – Cumulative counts derived from weekly data are available so refer to the Live Map! • 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.
Welcome to Week 4 for the 2025 growing season! This week includes: • Weather synopsis • Wireworms • Cutworms • Flea beetles • Alfalfa weevil • Cereal leaf beetle • Pea leaf weevil • Grasshopper diversity and scouting • Diamondback moth • Bertha armyworm • Cabbage seedpod weevil • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 4 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Cabbage stem flea beetle!
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.
The weekly average temperature for May 19 – May 25, 2025, across the Prairies was 11 °C which is slightly warmer than the long-term average. Temperatures were warmest in northern Alberta and coolest in southeastern Saskatchewan, southwestern Manitoba, and the east of the Rockies in Alberta (Figure 1). Overall, growing season average temperatures continue to climb as the first week of June approaches (Figure 2).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 19-25, 2025.Figure 2. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-May 25, 2025.
Between May 19 – 25, 2025, the prairie region received rain, starting on Victoria Day. Unfortunately, rainfall amounts generally did not exceed 15 mm (Figure 3). Edmonton and the southwest surrounding areas of Alberta (e.g., Yellowhead, Lac St. Anne, Brazeau, Parkland, Leduc, Lacombe, and Wetaskiwin Counties) received the greatest rainfall over the past week, whereas other areas of the Canadian prairies recorded less than 15 mm (Figure 3). So far this growing season, the majority of the prairie growing region has received an accumulation of less than 100 mm of cumulative rainfall between April 1 and May 25, 2025; Figure 4).
Figure 3. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of May 19-25, 2025.Figure 4. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-May 25, 2025.
Active Wildfires – Natural Resources Canada’s Canadian Wildland Fire Information System (CWFIS) creates and updates daily fire weather and fire behaviour maps year-round with hot spot maps updated daily between May and September. The website features three types of maps plus valuable links. Maps to access include: • Fire Weather • Fire Behaviour • Fire M3 Hotspotand example of the map for May 29, 2025, is copied below (Fig. 1).
Persons outdoors performing field scouting need to be aware of air quality arising from wildfire activity. Two online resources are available – both are updated daily and provide short video clips of forecasted ground level smoke conditions: • FireSmoke.ca (link to snip of short forecast video retrieved May 29, 2025 or Figure 2 for examples). • Firework (link to snip of forecast video retrieved May 29, 2025 or Figure 3 for examples).
Wireworms are the larval stage of click beetles from the family Elateridae. Click beetles, the adult stage, do not cause damage to crops. Wireworms live in the soil, where it can take 4 or more years to complete larval development. In the soil, wireworms feed on germinating seeds and the roots of a wide variety of prairie field crops including cereals, pulses, oilseeds, and vegetables including potato and carrots. Damage to root vegetables can result in unmarketable produce.
Several species of wireworms can be found on the Canadian Prairies but species commonly occurring in field crops are included in Figure 1. Even more importantly, there are four primary pest species, including Hypnoidus bicolor, prairie grain wireworm (Selatosomus aeripennis destructor), sugarbeet wireworm (Limonius californicus), and flat wireworm (Aeolus mellillus).
Figure 1. Dorsal views of economically important species of wireworms observed across the Canadian prairies and their adult click beetle. (Source: Guide to Pest Wireworms in Canadian Prairie Field Crop Production).
Similar to cutworms, bare patches in a field can be an early and obvious sign of wireworm infestation in the spring. Patchy crop emergence (Fig. 2), results when wireworms consume germinating seeds or feed on the roots and stems of young seedlings (Fig. 3).
Figure 2. A cereal field with patchy seedling emergence and stand establishment due to wireworm infestation. Picture by Dr. Haley Catton (AAFC, Lethbridge).Figure 3. Wireworm feeding damage on a faba bean seedling. Picture by Chris Baan.
Cutworm scouting spans April to late June across the Canadian prairies! Scout fields that are “slow” to emerge, are missing rows, include wilting or yellowing plants, have bare patches, or appear highly attractive to birds – these are areas warranting a closer look. Plan to follow up by walking these areas either very early or late in the day when some cutworm species (or climbing cutworms) move above-ground to feed. Start to dig below the soil surface (1-5 cm deep) near the base of symptomatic plants and also any healthy plants immediately adjacent to missing rows or wilting or clipped plants. Some cutworms feed while remaining just below the soil surface, clipping then pulling the plant below the soil surface as they munch away! If the plant is well-established (e.g., perennial grass or legume), check within the crown plus in the adjacent soil. The culprits could be cutworms, wireworms, or more!
Important: Several species of cutworms (Lepidoptera: Noctuidae) can be present in fields. They range in colour from shiny opaque, to tan, to brownish-red with chevron patterning. A field guide is available to help growers scout and manage the various species of cutworms that can appear in field crops grown on the Canadian prairies. Cutworm Pest of Crops is available free in either English or French! Download a searchable PDF copy to access helpful diagnostic photos plus a table showing which larvae are active at different points in the growing season!
Other vital resources to scout and manage cutworms include:
● For anyone on the Canadian prairies, Manitoba Agriculture’s Cutworms in Field Crops fact sheet includes suggested nominal thresholds for cutworms in several crops (Table 1). The same fact sheet describes important biological information, and provides great cutworm photos to support in-field scouting!
● For Albertans….. If you find cutworms, please consider using the Alberta Insect Pest Monitoring Network’s “2025 Cutworm Reporting Tool” then view the live 2025 cutworm map updated daily. Review the live map to see where cutworms are appearing then prioritize in-field scouting accordingly.
Flea Beetles (Chrysomelidae: Phyllotreta species) – Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Figure 1. Flea beetle feeding inflicted by overwintered adults including ‘shot-hole’ and stem feeding on seedling canola (B. napus). Photos: AAFC-Beaverlodge-Otani
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
If flea beetle densities are high, seedling damage levels can advance quickly – even within the same day! The cotyledon stage of canola is vulnerable to flea beetle feeding.
Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) to help estimate percent of leaf area consumed for canola seedlings – take Figures 2 and 3 scouting!
Figure 2. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).Figure 3. Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).
Flea beetles were the Insect of the Week (Wk 02 – May 13, 2024)! Additionally, access biological and pest management information posted by Saskatchewan Agriculture, or Manitoba Agriculture and Resource Development, or the Canola Council of Canada’s Canola Encyclopedia. Refer to the flea beetle page 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.
Prairie-Wide Monitoring: Annual grasshopper surveying is performed across western Canada by visually estimating densities in late summer. 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 pest species of grasshoppers were observed in 2024 are highlighted yellow, orange, or red in the geospatial map featured in Figure 1. Areas where historically higher densities of grasshoppers were observed in 2024 are worth prioritizing in 2025.
Figure 1. Densities of grasshoppers observed by visual in-field observations in late summer of 2024.
Grasshopper Scouting Tips: ● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species (Gavloski, Williams, Underwood, Johnson, Otani) to aid with field scouting from egg hatch and onwards. The PDF includes photos to help differentiate native versus pest grasshopper species plus froghopper, treehopper or even katydid species. ● It is best to scout on warm days when grasshopper nymphs are more active and easier to observe. ● Carefully check roadside ditches and along field edges but also check the edge of the crop and into the actual field. ● Younger or earlier instar nymphs are easier to manage – visit sites every few days to stay on top of local field conditions. ● A sweep-net can ‘detect’ grasshopper nymphs, however, economic thresholds for grasshoppers are based on the number of grasshoppers per square-metre counts. ● 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.
Important – A preliminary summary of available thresholds for grasshoppers has been kindly shared by Dr. J. Tansey (Saskatchewan Agriculture) in Table 1. When scouting, compare in-field counts to the available threshold value for the appropriate host crop AND for field or ditch situations. Available thresholds (nominal and economic) help support producers while protecting beneficials (i.e., predators, parasitoids, and pathogens) that regulate natural populations of grasshoppers.
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.
The annual pea leaf weevil survey is underway! The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge (Fig. 1).
Figure 1. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent-shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches. All photos courtesy of Dr. L. Dosdall.
In the spring, overwintered adults disperse to feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas). This feeding can produce a characteristic, scalloped (or notched) edges (Fig. 2). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Adult pea leaf weevil feeding and creating characteristic “notch” at edge of faba bean leaf. Photo: AAFC-Saskatoon-Williams.
The annual pea leaf weevil survey is conducted from late May to early June. The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge. Review the prairie-wide historical survey maps. Higher levels of feeding damage are correlated to higher pea leaf weevil densities so areas highlighted in Figure 3 warrant in-field monitoring in the spring of 2025.
Figure 3. Results of the annual pea leaf weevil survey conducted in the spring of 2024.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol. Access the Pea leaf weevil information posted by the Manitoba Pulse & Soybean Growers, Saskatchewan Agriculture, Alberta Agriculture and Irrigation, or the Prairie Pest Monitoring Network. Also refer to the pea leaf weevil page 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 Field Guides page.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 1). The green larva features a dorsal white line down the length of its body, has a dark brown head capsule, and will grow to 9 mm long.
Figure 1. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
Alfalfa growers are encouraged to check an updatedProtocol for Monitoring Alfalfa Weevil prepared by Guelly et al. 2025. 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” (2018; accessible in either English-enhanced or French-enhanced versions).
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 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 2022Jul28 but will be updated with 2025 reports as season progresses).
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.
Degree-days can be used to predict the timing of insect development and plan for pest scouting and management. Degree-days are calculated for different insect species using temperature thresholds specific to their development. Based on research, the temperature threshold for bertha armyworm (Mamestra configurata) development is 7 °C and 352 accumulated degree-days (base 7 °C) are required for overwintered pupae to begin their spring development phase. As of May 25, there are no areas on the prairies that have surpassed the degree-day requirement for pupal development of bertha armyworm (Fig. 1).
Figure 1. Growing degree-day heat units (Base 7 °C) accumulated across the Canadian prairies from April 1 to May 25, 2025.
Pheromone traps used to monitor bertha armyworm are typically set up along canola fields when pupal development reaches 75-80%; the 2024 monitoring season started the week of June 10, 2024. Cumulative counts from sentinel pheromone monitoring sites targeting bertha armyworm moths across the Canadian prairies in 2024 are highlighted as geospatial areas where producers are encouraged to prioritize in-field monitoring in 2025. Areas in Figure 2 highlighted yellow, orange, or especially red hosted pheromone traps that intercepted relatively high cumulative counts of moths in 2024 and should be prioritized for in-field scouting in 2025. Review the prairie-wide historical survey maps for this insect species.
Figure 2. Cumulative weekly counts of Bertha armyworm (Mamestra configurata) moths arising from the 2024 growing season.
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. Cumlative 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).
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 the 2019 Insect of the Week, which featured bertha armyworm and its doppelganger, the clover cutworm!
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to access their information as the growing season progresses:
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: • May 26, 2025 issue includes notification that pea leaf weevil survey has begun, continued flea beetle pressure and need to monitor seedling canola plus mustard, continuation of cutworm monitoring (and link to live cutworm map). • May 20, 2025 issue includes a recommendation to scout for grasshoppers, an update on flea beetle risk, and notice that diamondback moth reporting has begun. Also, AAI staff members have started surveying for pea leaf weevil in southern Alberta this week. • Cutworm live monitoring map for AB – Cumulative counts derived from weekly data are available so refer to the Live Map! • 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.
Welcome to Week 3 for the 2025 growing season! This week includes: • Weather synopsis • Flea beetles • Cutworms • Cereal leaf beetle • Pea leaf weevil • Grasshopper diversity and scouting • Diamondback moth • Bertha armyworm • Tick tips • Access PPMN-approved field guides • Crop production guide links • Provincial insect pest report links • Crop report links • Previous posts
Catch Monday’s Insect of the Weekfor Week 3 – This year features lesser-known insect pest species to help producers remain vigilant! Learn more about the Brown marmorated stink bug!
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.
Growing season temperatures cooled off slightly between May 12 and May 18, bringing the 7-day average temperature close to the long-term climate normals average for this time of the month (Fig. 1). The weekly average temperature for May 12 – May 18, 2025, across the Prairies was 10 °C. Temperatures were warmest in southeast Manitoba and cooler around the MB/SK border and the foothills region of Alberta (Figure 2).
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 12-18, 2025.Figure 2. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1-May 18, 2025.
The southeast corner of Saskatchewan and southwest corner of Manitoba received a good amount of rainfall over the past week, whereas other areas remained relatively dry (Fig. 3). As of May 18, a large portion of the prairie agricultural area has received less than 100 mm of cumulative rainfall this growing season (cumulative rainfall between April 1 and May 18; Fig. 4).
Figure 3. Seven-day average precipitation (mm) observed across the Canadian prairies for the period of May 12-18, 2025.Figure 4. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1-May 18, 2025.
Flea Beetles (Chrysomelidae: Phyllotreta species) – Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Figure 1. Flea beetle feeding inflicted by overwintered adults including ‘shot-hole’ and stem feeding on seedling canola (B. napus). Photos: AAFC-Beaverlodge-Otani
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
If flea beetle densities are high, seedling damage levels can advance quickly – even within the same day! The cotyledon stage of canola is vulnerable to flea beetle feeding.
Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) to help estimate percent of leaf area consumed for canola seedlings – take Figures 2 and 3 scouting!
Figure 2. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).Figure 3. Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).
Flea beetles were the Insect of the Week (Wk 02 – May 13, 2024)! Additionally, access biological and pest management information posted by Saskatchewan Agriculture, or Manitoba Agriculture and Resource Development, or the Canola Council of Canada’s Canola Encyclopedia. Refer to the flea beetle page 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.
Cutworm scouting spans April to late June across the Canadian prairies! Scout fields that are “slow” to emerge, are missing rows, include wilting or yellowing plants, have bare patches, or appear highly attractive to birds – these are areas warranting a closer look. Plan to follow up by walking these areas either very early or late in the day when some cutworm species (or climbing cutworms) move above-ground to feed. Start to dig below the soil surface (1-5 cm deep) near the base of symptomatic plants and also any healthy plants immediately adjacent to missing rows or wilting or clipped plants. Some cutworms feed while remaining just below the soil surface, clipping then pulling the plant below the soil surface as they munch away! If the plant is well-established (e.g., perennial grass or legume), check within the crown plus in the adjacent soil. The culprits could be cutworms, wireworms, or more!
Important: Several species of cutworms (Lepidoptera: Noctuidae) can be present in fields. They range in colour from shiny opaque, to tan, to brownish-red with chevron patterning. A field guide is available to help growers scout and manage the various species of cutworms that can appear in field crops grown on the Canadian prairies. Cutworm Pest of Crops is available free in either English or French! Download a searchable PDF copy to access helpful diagnostic photos plus a table showing which larvae are active at different points in the growing season!
Other vital resources to scout and manage cutworms include:
● For anyone on the Canadian prairies, Manitoba Agriculture’s Cutworms in Field Crops fact sheet includes suggested nominal thresholds for cutworms in several crops (Table 1). The same fact sheet describes important biological information, and provides great cutworm photos to support in-field scouting!
● For Albertans….. If you find cutworms, please consider using the Alberta Insect Pest Monitoring Network’s “2025 Cutworm Reporting Tool” then view the live 2025 cutworm map updated daily. Review the live map to see where cutworms are appearing then prioritize in-field scouting accordingly.
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.
The annual pea leaf weevil survey is getting started! The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge (Fig. 1).
Figure 1. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent-shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches. All photos courtesy of Dr. L. Dosdall.
In the spring, overwintered adults disperse to feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas). This feeding can produce a characteristic, scalloped (or notched) edges (Fig. 2). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Adult pea leaf weevil feeding and creating characteristic “notch” at edge of faba bean leaf. Photo: AAFC-Saskatoon-Williams.
The annual pea leaf weevil survey is conducted from late May to early June. The survey is conducted by counting the characteristic ‘u’ shaped feeding notches made by adult pea leaf weevil at several locations along the field edge. Review the prairie-wide historical survey maps. Higher levels of feeding damage are correlated to higher pea leaf weevil densities so areas highlighted in Figure 3 warrant in-field monitoring in the spring of 2025.
Figure 3. Results of the annual pea leaf weevil survey conducted in the spring of 2024.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol. Access the Pea leaf weevil information posted by the Manitoba Pulse & Soybean Growers, Saskatchewan Agriculture, Alberta Agriculture and Irrigation, or the Prairie Pest Monitoring Network. Also refer to the pea leaf weevil page 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 Field Guides page.
Grasshopper Scouting Tips: ● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species (Gavloski, Williams, Underwood, Johnson, Otani) to aid with field scouting from egg hatch and onwards. The PDF includes photos to help differentiate native versus pest grasshopper species plus froghopper, treehopper or even katydid species. ● It is best to scout on warm days when grasshopper nymphs are more active and easier to observe. ● Carefully check roadside ditches and along field edges but also check the edge of the crop and into the actual field. ● Younger or earlier instar nymphs are easier to manage – visit sites every few days to stay on top of local field conditions. ● A sweep-net can ‘detect’ grasshopper nymphs, however, economic thresholds for grasshoppers are based on the number of grasshoppers per square-metre counts. ● 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.
Important – A preliminary summary of available thresholds for grasshoppers has been kindly shared by Dr. J. Tansey (Saskatchewan Agriculture) in Table 1. When scouting, compare in-field counts to the available threshold value for the appropriate host crop AND for field or ditch situations. Available thresholds (nominal and economic) help support producers while protecting beneficials (i.e., predators, parasitoids, and pathogens) that regulate natural populations of grasshoppers.
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.
Degree-days can be used to predict the timing of insect development and plan for pest scouting and management. Degree-days are calculated for different insect species using temperature thresholds specific to their development. Based on research, the temperature threshold for bertha armyworm (Mamestra configurata) development is 7 °C and 352 accumulated degree-days (base 7 °C) are required for overwintered pupae to begin their spring development phase. As of May 18, much of the prairies has not reached the degree-day requirement for pupal development of bertha armyworm (Fig. 1).
Figure 1. Growing degree-day heat units (Base 7 °C) accumulated across the Canadian prairies as of May 18, 2025.
Pheromone traps used to monitor bertha armyworm are typically set up along canola fields when pupal development reaches 75-80%; the 2024 monitoring season started the week of June 10, 2024.
Figure 2 includes photos of the various life stages of the bertha armyworm. There is one generation per year and pupae overwinter in the soil (Fig. 2, C). Each growing season, green unitraps utilizing pheromone lures are deployed and checked weekly over a 6-week window. Cumlative 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 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C), to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).
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 the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Public Health Agency of Canada has a Top 10 Tick Hiding Spots on Your Body available as a poster in multiple languages including Mi’kmaq, Mohawk, Ojibwe (Eastern), French, English, Spanish, Tagalog, Arabic, Punjabi, Chinese (simplified and traditional), and Italien. An example in English is posted below for your quick reference (Fig. 1) so check it, then yourself, and your pets!
Figure 1. Screenshot of Public Health Agency of Canada’s infographic of top 10 tick hiding spots on your body (2020; retrieved 2024May23).
Another good resource is the free eTick APP which is a public platform for image-based identification and population monitoring of ticks in Canada. Both Google Play and iOS versions of the App enable users to upload tick photos for help with identification.
Continued surveillance is important and enables tracking of Lyme disease incidence and risk. Follow the links to learn more about Lyme disease and ticks if you live in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, or Quebec. Access additional information posted by Health Canada related to Lyme disease surveillance, which also summarized that a preliminary review of data revealed a total of 5239 cases of Lyme disease were reported in 2024 to provincial public health units across Canada.w the links to learn more about Lyme disease and ticks if you live in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, or Quebec. Access additional information posted by Health Canada related to Lyme disease surveillance which also summarized a preliminary 2024 total of 5239 cases of Lyme disease were reported to provincial public health units across Canada.
In addition to being free, the downloadable PDF versions of these guides are searchable. All include descriptions of insect biology, helpful diagnostic photos, plus tips related to when and how to scout for important economic pests of western Canada’s many field crops.
Here’s one of the five guides we highly recommend but there’s also guides for wireworm pest species, cutworm pest species, cow patty insects plus the pests & predators field guide! Find them all here to download!
Every year, these guides are updated with product information and so much more! Hard copies can be purchased via the above websites but also look for the download button to access FREE downloadable PDF copies!
A few other helpful tools to keep at your finger tips:
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to access their information as the growing season progresses:
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: • May 20, 2025 issue includes a recommendation to scout for grasshoppers, an update on flea beetle risk, and notice that diamondback moth reporting has begun. Also, AAI staff members have started surveying for pea leaf weevil in southern Alberta this week. • Cutworm live monitoring map for AB – Cumulative counts arising from weekly data are available so refer to the Live Map which already cites 2025 reports! • Diamondback moth pheromone trap live monitoring map for AB – Cumulative counts arising from weekly data are now being generated so refer to the Live map.
As the growing season progresses, the Weekly Update topics move on and off the priority list for in-field scouting. We provide the list below to support season-long monitoring. Click to review these earlier 2025 Posts (organized alphabetically): • 2024 Risk maps (Wk 02) • Field heroes (Wk 02) • Scouting charts – canola and flax (Wk 03 of 2022)
