In laboratory experiments, we determined the effects of a number of defoliants (Def, Dropp, and Harmony) alone and in combination with insecticides [Guthion at (0.25, 0.125, and 0.0625) lb AI / ac; and Karate at
(0.066, 0.033) lb AI/ac] on boll weevil mortality in relation to age, sex, weight, body fat, and on number of eggs oviposited per female per day. Both direct (weevils hit by spray) and indirect (weevils exposed to leaves which had been sprayed) treatment effects were examined. The weevils used in the first set of experiments were from the Gast colony and were reared on artificial diet, and those in the second set were reared from infested squares collected in cotton field in the Lower Rio Grande Valley of Texas. In both sets, weevils were tested at 3 and 14 days old. The results indicated that Def alone exhibited a toxic effect on boll weevil. Def + Karate (0.0.33 lb AI/ac), and Def + Guthion (0.125 lb AI/ac) showed synergistic effects on mortality. Although weevils that died from chemical treatments weighed less than survivors, young weevils that were near death had more developed fat bodies than survivors. Effects of Def + Karate (0. 033 lb AI/ac), and especially Karate alone at 0. 066 lb AI/ac on boll weevil were manifested through a significant reduction in the number of eggs deposited per female per day.