In the spring, young overwintering larvae feed on developing buds and then bore into young tender shoots. Newly hatched first generation larvae feed on buds and newly set nuts. Infested nuts are held together by a cluster of silken threads. They are easily recognized by the frass cast out by the larvae. A single larvae may destroy from one to all of the nuts in a cluster.
Losses vary considerably from year to year.
A light infestation in heavy crop years may provide desirable thinning, but in light crop years, most or all of the nuts may be destroyed. The larvae become active about bud break in the spring. They feed on buds for a short time, then burrow into tender young shoots. Larvae pupate in tunneled shoots or in cocoons that they attach to other parts of the tree. The F-1 generation of moths emerge in May and are most numerous about the time that nuts are setting.