Fig. 1.

Average number of broad-spectrum insecticide applications in nonTr, Bt, and BtHr cotton (with 95% confidence intervals). The number of insecticide applications was significantly higher in nonTr than in transgenic cotton in 2002 (one-tailed contrast, t = 4.13, df = 72, P < 0.0001) (a) and in 2003 (one-tailed contrast, t = 1.99, df = 72, P = 0.025) (b). The number of insecticide applications was higher in 2003 than in 2002 (P = 0.058), although differences in insecticide applications among cotton types did not vary between years (P = 0.47).