Efficacy of Selected Insecticides Against Cotton Aphid on Cotton, 1997A

Two tests were conducted to evaluate the efficacy of selected insecticides against cotton aphids in non-irrigated Bt cotton planted 1 May in Test 1 and 5 May in Test 2. Plots consisted of 4 rows (40-inch centers) X 50 ft. Treatments were arranged in a RCB design with 4 replications. No foliar insecticides were applied to the plots before the test was initiated. Prior to treatment, cotton plants with infestations of cotton aphids in the plant terminals (20/plot) were marked with plastic tags. Treatments were applied to Test 1 and 2 on 25 and 30 Jun, respectively. In both tests, insecticides were applied with a handboom and CO2-charged system calibrated to deliver 10 gpa through Teejet 8002 flat fan nozzles (2/row) at 28 psi. Treatment efficacy was evaluated by sampling 10 tagged plant terminals (all apical shoot growth above and including the first fully expanded leaf) from each plot at 2 and 7 DAT. Treatments were evaluated in Test 1 on 27 Jun (2 DAT) and 2 Jul (7 DAT) and in Test 2 on 2 Jul (2 DAT) and 7 Jul (7 DAT). Cotton aphids were washed from the plant foliage onto 300-mesh wire sieves, backwashed into ruled filter paper (7 cm), and counted using a binocular dissecting scope. Plots, in both tests, received 0.11 and 1.98 inches rainfall on 29 Jun and 6 Jul, respectively. Data were analyzed with ANOVA and means were separated according to DMRT.