The mandated change of long season cotton to a short season system for pink bollworm (PBW) and other insect control in 1988 in the Imperial Valley may alter the strategy of eliminating green bolls which host PBW overwintering diapause larvae. In this study seven defoliant treatments were examined with respect to their effect on lint yield, leaf defoliation and reduction of immature green bolls. The treatments consisted of four defoliant chemicals (Def^®, Dropp^®, Tumbleaf^®, and Cotton Aid^®) and two other chemicals (Prep^® and Accelerate). Results indicated that Dropp^® treatments had significantly better cotton defoliation than other four treatments in the 1987 study. The possibility of taking advantage of the high air temperature and solar radiation in the valley to promote the opening of green bolls is discussed.