During 1996 and 1997 we examined the consequences of June-early July insecticidal applications on predacious arthropods, later development of the cotton bollworm (Helicoverpa zea), extent of damage, and effects on crop maturity and yield. Although research included conventional cotton, emphasis was on effects of beneficials on H. zea threshold development in B.t. cotton. Large fields (on-farm) were planted half to ‘DPL 5415' and half to ‘NuCOTN 33b' with half of each cultivar treated with acephate to "mimic" applications for plant bugs or other pests. These early applications decimated predacious arthropods, and consequently caused several-fold increases in cotton bollworm, fall armyworm (Spodoptera frugiperda) and boll damage. In B.t. cotton, without rigid control of bollworm, yields were reduced and maturity was delayed rather than advanced by early applications of acephate. In South Carolina, insecticides are seldom needed between the seedling stage and the mid-July flight of bollworm into cotton from corn. In other areas of the cotton belt where early applications are necessary for the boll weevil (Anthonomous grandis grandis), plant bugs or aphids, the effects on beneficials and subsequent pest development should be considered.