• Peas
• Agriculture and Agri-Food Canada
• Pest Management
• Yields

Objective

To determine the overwintering biology of pea leaf weevil populations in southern Saskatchewan. To assess foliar/nodule damage and yield in field peas in response to seed coat and foliar insecticides in a field plot study. To compare on-farm yields of treated and untreated seed to develop and validate action thresholds for pea leaf weevil in field peas. To obtain baseline data on aphids and their natural enemies in pulse crops to aid in future development of action thresholds.

Outcome

Weevils emerged from around their secondary host plants, such as alfalfa after the winter, and their peak trap capture in the spring coincided with warming daily temperatures in mid to late May. In the laboratory, new generation adult weevils were exposed to a range of temperatures typical to winter conditions on the prairies; weevils died within 30 days when exposed to daily mean temperatures of -10˚C. Less mortality was observed at warmer temperatures similar to those expected with insulation provided by snow and soil. When weevil densities were high enough to inflict damage on field peas, the systemic insecticide effectively prevented feeding damage by adult and larval weevils and protected yields. The foliar insecticide application had no effect on pea leaf weevil damage to field peas and probably is a poor management option. In a field scale experiment, weevil densities were highly variable at the sites in both years, but preliminary analyses indicate that when weevil densities were moderate, the systemic insecticide prevented feeding damage by adult and larval weevils. Pea aphid populations fluctuated between years due to the migratory nature of this pest, but when aphids were present, so were their natural enemies, including lady beetles, green lacewings, damsel bugs, minute pirate bugs, and parasitoids. This information will be used to guide the development of future research projects focused on pea aphid management in Saskatchewan.

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