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Remember – the rate of development and timing of adult midge emergence varies at the field level and can only be verified through in-field scouting. Midge flight coinciding with the beginning of anthesis is a crucial point when in-field counts of wheat midge on plants are carefully compared to the economic thresholds.
Producers opting to grow cultivars susceptible to wheat midge need to be mindful that any historically elevated density of wheat midge occurring over the past one or even possibly six years across the prairies that also has received substantial rainfall since May of 2024, warrants in-field monitoring now. Review the past wheat midge maps here in relation to your fields THEN compare the historical densities to areas of high precipitation in Figure 1.
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.
Grasshopper Scouting Tips: ● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species to aid in-field scouting from egg hatch and onwards. ● 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.
Access the Provincial Insect Pest Report for Wk09 for updates for this economic insect pest.
Scouting and pest management for diamondback moth depends on in-field counts of larvae per metre2! This means plants need to be pulled and tapped off to assess the number of larvae! Use Figure 1 below to help identify the different stages of the diamondback moth.
Figure 1. The life stages of the diamondback moth (Plutella xylostella), which can have multiple generations per year. Photos: AAFC-Saskatoon-J. Williams.
The economic threshold for immature and flowering canola is 100-150 larvae per metre2.
Access the Provincial Insect Pest Report for Wk11 for updates for this economic insect pest.
Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Access the Provincial Insect Pest Report for Wk09 for updates for this economic insect pest.
Remember: in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. Use the images below (Fig. 1) to help identify moths from the by-catch that will be retained in the green phermone-baited unitraps.
Figure 1. 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.
Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:
Jennifer Otani, Shelby Dufton, Amanda Jorgensen and Shelley Barkley
Categories
Week 11
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).
Jennifer Otani, Hector Carcamo and Meghan Vankosky
Categories
Week 11
On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.
Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.
Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps.In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.
Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).
Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.
Scouting tips to keep in mind: Begin monitoring canola when it bolts and 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.
Scouting for canola flower midge tends to be easiest as the flowering stage of canola ends and pod development begins. Female canola flower midge lay eggs on developing canola buds and larvae develop inside the buds, resulting in galled flowers that do not open or produce pods.
Although canola flower midge does not appear to occur at densities that cause economic damage, scouting for canola flower midge will help to monitor population growth at the local scale to avoid surprises in the future. The monitoring protocol used during our survey from 2017-2019 is now available online so that everyone can scout for canola flower midge.
Check out the Canola Flower Midge Scouting post from Week 10 in 2023 for pictures of damage caused by this insect and to see a map of canola flower midge distribution.
Jennifer Otani, Carter Peru, James Tansey, John Gavloski and Shelley Barkley
Categories
Week 11
Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to readily access their information as the growing season progresses:
MANITOBA’SCrop Pest Updates for 2024 are available. Access the online July 18, 2024 report (or PDF copy). Bookmark the insect pest homepage to access fact sheets and more! Highlights pulled from the latest report include: • Aphids – Dr. J. Gavloski reported, “control of aphids in field peas from the Southwest (Boissevain area), and Central region (Notre Dame de Lourdes, Starbuck and Fannystelle areas)”. Access the Aphids on Peas fact sheet. • True armyworm – Reports that, “true armyworms remain at high levels in some areas, and control was reported from the Interlake and Central regions. There is also some evidence of parasitism of true armyworms starting to become visible (pupal clusters of a parasitic wasp called Cotesia).” Access the PDF copy of the July 10 report. • Grasshoppers– Reports, “some grasshopper control in soybeans and cereal crops occurred in the Central region”. • Sunflower bud moth – “Has been noticeable in many sunflower fields” and is featured in the July 18th report. • Bertha armyworm pheromone trap monitoring – Reports moths in “66 of 79 traps” although “counts have been low so far”. Where present, “eggs are now starting to hatch”. Access the PDF copy of the July 10 report. • Diamondback moth pheromone trap monitoring – Trapping is complete for 2024 (as of Wk 09; access the PDF copy of the July 4 report).
SASKATCHEWAN’SCrop Production News is back for the 2024 growing season! Access the online Issue #4 report which includes sections covering thrips in small grains cereal crops, cabbage seedpod weevil, and mid-season gopher control. Bookmark their insect pest homepage to access important information! • Insect pests to watch – A brief summary of the week was provided by Dr. J. Tansey (as of July 17) – “The prevalent story this week was pea aphid in lentils. Diamondback moth larvae were numerous in a smattering of fields in the southwest and monitoring is warranted. A few pockets of grasshoppers remain in southwest and east-central regions of Saskatchewan and populations of two-striped are reaching adulthood this week.” • Diamondback moth – Pheromone trapping is complete for 2024 and can be reviewed online. A total of 24 sites intercepted a cumulative total of ≥25 moths so in-field monitoring for larvae should be prioritized in those areas. • Bertha armyworm – Cumulative catches in phermone-baited unitraps “continue to increase slowly with one trap in east central reporting more than 300”. • Also access the Crops Blog Posts that released a grasshopper activity update (June 2024), announced registration for the Crop Diagnostic School 2024 but also posts help for scouting fields for wireworms (May 2024), grasshopper identification: pest or not (Apr 2024), a summary of wheat midge populations and management (Mar 2024), and a description of pea leaf weevil populations (Feb 2024).
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 occasionally includes insect-related information, e.g., scout for wheat midge (July 15, 2024), the right canola crop stage to spray for lygus bugs (July 8, 2024), soil moisture, wheat midge and other insect pests (June 24, 2024), scout for grasshoppers and other insect pests (June 17, 2024); how to manage stem feeding from flea beetles, keep canola bins malathion-free, scout for grasshoppers and other pests (June 10, 2024); scout for insect pests (June 3, 2024); scout for grasshoppers (May 27, 2024); flea beetle control (May 6, 2024); cereal insect pests, latest on insects in canola, and post-emergence wireworm scouting (May 13, 2024). • Wheat midge monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. Shelley Barkley reported that, “midge numbers are increasing in the Edmonton and Peace region”. So far, cumulative trap counts from 35 trap locations are reporting; 10 sites in central Alberta are “high” and in the Peace River region 21 sites are reporting “high”, 2 sites are “medium”, and 2 sites are “low” (as of July 18, 2024). • Cabbage seedpod weevil monitoring – Sweep-net count data can be reported here then the data populates the Live Map. So far, a total of 16 sites in southern Alberta are reporting; there are 14 “low risk” plus 2 “high risk” reports as of July 18, 2024). • Bertha armyworm pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. Cumulative trap counts from 265 trap locations are all reporting “low risk” while 1 trap location near Vulcan plus 1 trap location near Lethbridge are both reporting “medium risk” as of July 18, 2024). • Diamondback moth pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. Cumulative trap counts have been recorded from 32 reporting sites and 28 remain in the “no risk” category as of July 4, 2024). Four trap locations have caught > 25 adult diamondback moths; sites fall within the County of Grande Prairie (as of June 8, 2024), County of Warner (as of June 15, 2024), Vulcan County (as of June 15, 2024), and County of Barrhead (as of June 15, 2024). • Cutworm live monitoring map – Cumulative counts arising from weekly data are available so refer to the Live Map. So far, 10 surveyed sites have reported from across the province, nine falling within southern Alberta and one report from the County of Grande Prairie.
