Efficacy of Selected Insecticides Against Cotton Aphids on Bt Cotton, 1996

Abstract

Abstract Three tests were conducted to evaluate the efficacy of selected insecticides against cotton aphids in non-irrigated Bt cotton planted 1 May. Plots consisted of 4 rows (40 inch centers) X 50 ft. Treatments were arranged in a RCB design with 4 replications. No insecticides had been previously applied to the test areas. Treatments were applied to Test 1 on 19 Jun, Test 2 on 24 Jun and Test 3 on 25 Jun, respectively. In Test 1, insecticides were applied with a tractor-mounted boom and compressed air system calibrated to deliver 10 gpa through Teejet 80015 flat fan nozzles (2/row) at 34 psi. In Tests 2 and 3 insecticides were applied with a hand-boom and compressed air system calibrated to deliver 10 gpa through Teejet 80015 flat fan nozzles (2/row) at 24 psi. Treatment efficacy was evaluated by sampling ten plant terminals (all apical shoot growth above and including the first fully expanded leaf) from each plot. Treatments were evaluated in Test 1 on 21 (2 DAT) and 26 Jun (7 DAT), Test 2 on 27 Jun (3 DAT) and 1 Jul (7 DAT), and Test 3 on 28 Jun (3 DAT) and 2 Jul (7 DAT). Cotton aphids were washed from the plant foliage onto 300 mesh wire sieves, backwashed onto ruled filter paper (7 cm), and counted using a binocular dissecting scope. These plots received 0.30, 0.87, 0.03 and 0.08 inch rainfall on 19, 20, 22, and 24 Jun, respectively. Data were analyzed with ANOVA, and means were separated according to DMRT.