Looks like most, if not all, of us should be on alert for corn earworms/bollworms in our fields. We’re seeing an increasing number of growers at R2-R3 growth stage having treatment level—or just below. Scout your beans, particularly those not yet lapped, for developing infestations.
Bollworms can seriously reduce soybean yields since they feed directly on beans by eating a hole in the pod and consuming the seed. Large caterpillars may be green, brown or yellow. The body is stocky, and the head is usually pale brown or orange. Light and dark stripes run the length of the body. The larva has four pairs of abdominal prolegs. Young blooms and tender leaves are sometimes eaten. Beans should be checked during flowering and early pod set.
The suggested treatment threshold for corn earworm based on sweep-net sampling is below. To determine the treatment level, estimate the potential value of the crop and the cost of the insecticide application. For example; if the crop value is $8/bushel and the cost of control is $14/acre, including application costs, the sweep-net threshold would be 8.6 larvae per 25 sweeps.
Hang on to the following worm identification chart for reference as you scout.