Relationship between bollworm (Lepidoptera : Noctuidae) pheromone trap catches and yield differences in sprayed and nonsprayed BT cotton

Data from field trials froth 1990 to 1999 with Bt cotton and bollworm, Heli coverpa zea (Boddie), pheromone traps were utilized to determine relationsh ips between yield differences of sprayed and nonsprayed Bt cotton lines and bollworm moth activity as determined by adult collections in wire cone sex pheromone-baited traps. Data based on accumulated trap catches were examin ed for six periods: June, July, August, June through July, July through Aug ust, and June through August. Highly significant linear correlations were o bserved for the July, July through August, and June through August periods with r(2) values of 0.70, 0.87, and 0.76, respectively. Of the quadratic an d cubic relationships between yield differences and trap catches, the only significant correlation was a quadratic relationship for the August time pe riod (r(2) = 0.73). The study demonstrates the importance of bollworm contr ol in Bt cotton during periods of high bollworm pressure.