Scout for Thistle Caterpillars, Aphids, Soybean Gall Midge

Farmers have seen several soybean insects show up in fields this summer in Iowa. These pests include thistle caterpillars, soybean aphids and soybean gall midge.

Soybean fields have been invaded by unusually high populations of thistle caterpillars, which defoliate soybean leaves. It is recommended that soybean growers apply a foliar insecticide if damage exceeds 20% per plant after plants reach reproductive stage. If you have caterpillar feeding damage before bean plants are in reproductive growth stage, the treatment threshold is 30% defoliation per plant.