There are generally few early season insects we need to worry about in pulse and soybean crops grown in Manitoba. These include wireworms, seedcorn maggot and cutworms. Of these insects, insecticide seed treatment will provide potential control of only wireworms and seedcorn maggot. However, it is important to scout for all three of these insects from May to June, as the crop is emerging and just after emergence. Knowledge of pest pressure may help with crop management decisions for the following year.
Wireworms
Wireworm scouting checklist:
✅ Assess pulse and soybean crops from planting to V3 (May to June).
✅ Target fields with a history of wireworm infestations, recent cultivation of grassland or sandy to silty soil texture.
✅ Inspect areas of fields with wilted plants or thin stands.
✅ Dig into the soil of affected areas to assess damage to germinating seeds, underground parts of young seedling stems and roots.
✅ Set out at least 4 bait traps in early spring to assess wireworm population.
✅ If found, collect a sample and contact John Gavloski (gavloski@gov.mb.ca) and Bryan Cassone (cassoneb@brandonu.ca).
Seedcorn maggot
Seedcorn maggot scouting checklist:
✅ Assess pulse and soybean crops from planting to VE (May to mid-June).
✅ Target fields that were planted early, those with cold, wet soil, recent tillage or incorporation of plant material, recent manure application and sandy to silty soil texture.
✅ Inspect areas of fields with wilted plants or thin stands.
✅ Cut open suspect seeds or seedling stems.
✅ If found, collect a sample and contact John Gavloski (john.gavloski@gov.mb.ca) or MPSG.
Cutworms
Cutworm scouting checklist:
✅ Assess pulse and soybean fields on a weekly basis from May to June.
✅ Inspect areas of fields with wilted, yellow or missing plants.
✅ Gently dig around damaged plants within the top 10 cm of soil to find cutworms. Scoop soil into a container and shake potential larvae loose.
✅ If found, identify the species and contact John Gavloski (gavloski@gov.mb.ca) or MPSG.
✅ Click here for more information on cutworm scouting in pulse and soybean crops.
Pea Leaf Weevil
Pea leaf weevil scouting checklist:
✅ Assess field pea and faba bean fields from V2 to V3 in late May and early June.
✅ Look for leaf notching, a sign of adult weevil feeding.
✅ Gently disturb the soil surface around damaged plants to find adult weevils.
✅ If found and captured, contact John Gavloski (gavloski@gov.mb.ca) or MPSG for species identification.
✅ Click here for more information on the pea leaf weevil.
Insects Not Yet Confirmed in Manitoba
Two early-season insects that have not yet been confirmed in Manitoba is the bean leaf beetle and european chafer. They are on the insecticide seed treatment label for soybeans, but their presence is not yet suspected in Manitoba.
Additional Resources
Field Crop and Forage Pests and their Natural Enemies in Western Canada – AAFC
Prairie Pest Monitoring Network
Cutworm Pests of Crops on the Canadian Prairies – AAFC
Cutworms in Field Crops – Manitoba Agriculture
Soybean Insect and Disease Scouting Calendar