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.
Dylan Sjolie, Tamara Rounce, Meghan Vankosky and Jennifer Otani
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Week 6
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.
Dylan Sjolie, Meghan Vankosky, Tamara Rounce and Jennifer Otani
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Week 6
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.
Dylan Sjolie, Tamara Rounce, Jonathon Williams, Meghan Vankosky and Jennifer Otani
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Week 6
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!
Jennifer Otani, Haley Catton, Wim van Herk and Julien Saguez
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Week 6
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.
Jennifer Otani, Kristen Guelly, Jennifer Retzlaff, Adele Beaudoin, Boyd Mori and Julie Soroka
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Week 6
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 2024 Monarch Migration Map! A screenshot of Journey North’s “first sightings of adults” map was featured last week. This week, the map of “first sightings of LARVAE” has been placed below (retrieved 27Jun2024) but follow the hyperlink to check the interactive map. Larvae have been spotted in Manitoba so far!
Jennifer Otani, John Gavloski, James Tansey, Amanda Jorgensen and Shelley Barkley
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Week 6
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.
