The fourth and fifth instars are green to gray, with two black spots and several smaller white spots on each segment. Heavily infested leaves may be reduced to a network of veins. Most damage occurs in the top third of plants. Severe defoliation may cause bolls to open prematurely, and also cause shedding of squares and small bolls. The use of Bt cotton.
Infestations usually begin at the edges of a field or in sandy streaks where plants are stressed.
Check these areas first for damage to upper leaves. Treatment timing is critical because sprays cannot reach leafmining instars or horseshoe-stage larvae. If infestations are severe, wait until most larvae are in the horseshoe stage, then spray within 2 days to kill the fifth instars when they emerge from their shelters. Spot treat infestations that are limited to certain parts of the field. The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies.