Larvae become fully developed in three or four weeks and then burrow three to four inches in the soil to pupate. In about three weeks the pupae transform into adult moths and another generation begins. Expect one to four generations per year. Plants can tolerate some feeding, but if the larvae become a problem, remove them by hand. Bacillus thuringiensis is an effective biological agent on small larvae.
Braconid wasps are an important natural enemy.
Plowing in late winter will reduce the number of overwintering pupae in the soil. Other insecticides are available.