Corn earworm, often called soybean podworm, can be a problem in late-planted or double-cropped soybeans. Corn earworm larvae are about 1.5 inches long with lines down the back of their pink, green, cream, or yellow backgrounds.
Worms attack all parts of the soybean plant, but economic concerns are focused on worms feeding on reproductive structures (blooms, pods and young seeds). Infestations during peak flowering to early pod fill are of the most importance economically. Corn earworms move through the landscape from weeds to corn to cotton to soybeans. Corn is the most preferred host and when corn planting is staggered like it is this year, they may move from corn to corn and be light in other crops.
According to the Missouri Pest Management Guide: Treat when defoliation reaches 30% prebloom or 20% from bloom to pod fill or when larval numbers exceed one per foot of row and 5% or more of pods are damaged. Heavy populations may cause excessive defoliation and pod loss.