The effects of natural enemy conservation versus disruption and early versus late planting dates on the larval population development of caterpillar pests, fruit damage, and yield were examined in pure and blended genotypes of BollgardTM B.t. cotton and in non-B.t. cotton. Percent (%) larval infestation and % damaged fruit were higher in disrupted plots than in conserved plots. Disrupted plots of 0% B.t.: 100% non-B.t. yielded significantly less than conserved plots of the same seed blend, but disrupted plots of the remaining seed blends had higher yields than their respective conserved plots. Mean % larval infestation and % damaged fruit were higher in early-planted cotton than in late-planted cotton, but early-planted cotton yielded significantly higher than late-planted cotton. As the percentage of B.t. seed in the blends decreased, numbers of live larvae and damaged fruit increased, and yields were reduced. Overspraying 100% B.t.: 0% non-B.t. cotton with lambda cyhalothrin resulted in significant reductions in % larval infestations and % damaged fruit and an increase in seed cotton yield.