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Agronomic Watch

Cutworms & Canola Flea Beetles

CUTWORMS ACTIVE
As newly planted crops start to emerge, it is time to start routine scouting for cutworms. Cutworms damage plants in the larval stage (caterpillar) and cause plant injury by cutting stems near the soil line, chewing on the foliage and reducing plant stands. Cutworms often will move down a row as they continue to feed on plants. Cutworms can do significant feeding injury during the early growth stages (seedling through 4-6 leaf stage) of field crops. Routine scouting for cutworm larvae is best in the evening, since they feed at night and hide underneath clumps of soil and debris during the day. If you find cut off plants, dig around these plants about two or more inches deep, and search for cutworms. When disturbed, cutworms curl up into a ‘C-shape.’ Row crops, such as soybean, canola, lentils, field peas and sunflowers, are more susceptible to cutworm damage than small grains, because cut plants do not grow back (grains compensate by tillering). Continue scouting until early July for late season cutworms or until crops have advanced beyond the susceptible period (seedling through 4-6 leaf stage). An evening application is recommended to target the peak feeding of cutworms at night.

    • Canola – 1 larva per square foot
    • Sunflower – 1 larva per square foot or 25-30% stand loss


CANOLA FLEA BEETLES FEEDING ACTIVITY INCREASING
The recent stretch of dry, warm sunny weather has flea beetles hoppin’ and poppin’ in canola! Scout canola fields now and regularly in the next few weeks for flea beetle feeding, especially in canola from the cotyledon through 6-leaf stages. The higher the feeding pressure, the more frequently fields should be scouted. The cool, wet weather we had in mid-May in most of ND either delayed canola planting or slowed growth of canola that did get planted. Consequently, canola is in early growth stages that are most susceptible to flea beetle feeding injury. Insecticide seed treatment failure is a possibility, especially in earlier planted canola that experienced delayed growth. Economic feeding injury to seedlings will result in delayed plant development for the remainder of the growing season. When scouting, look for the presence of striped and crucifer flea beetles, and examine the cotyledons and emerging leaves closely for pitting and shot holes. A foliar treatment is warranted if 20-25% defoliation has occurred on seedlings through the 6-8 leaf stage.

For more details about either of these insects or other crops refer to the NDSU Crop & Pest Report: NDSU Crop & Pest Report – June 9, 2022