July is when the prairies start to get a taste of what summer actually is: warm weather, thunderstorms, and bugs. In agriculture, these summer forces can make or break the crop year. Insects can be negative or positive, and in pulse crops, the insect of interest is aphids.
These small, green pests overwinter their eggs in tall clover and alfalfa, and the young then move into the crops. The majority of the aphids seen in the prairies are blown in from the states. Because the insects are able to move from birth to maturity from 5-50 days and are able to asexually reproduce, one growing season can bring up to 15 generations of aphids. As innocent as they may look, they directly impact yield by sucking the sap from the plant. This weakens the overall plant health and reduces seed size, in turn, reducing overall yield.
Scouting is done in the late stages of vegetative growth until the mid-reproductive stage. Using a sweep net towards the center of the field, this can determine if the population has surpassed the economic or nominal threshold. In peas, the threshold is 9-12 aphids per sweep at flowering, and in lentils, insecticide use is recommended at 30-40 aphids per 180 degree sweep.
Thresholds and Biological Control
These thresholds can be raised easily given biological controls are present in the field. Unluckily for aphids, there are some very effective biological controls in Saskatchewan. Ladybugs, parasitic wasps, lacewings, and damsel bugs are notable natural enemies of aphids. An increased presence of these insects could be adequate control of the pests, and if the aphid population does not increase within a two day period, spraying may not be necessary.
If you have questions about aphids in your pulses, call your local Synergy AG, and an Agronomist would be happy to help your crop to be a clean sweep!
Karly Rumpel A.Ag.