Apple, Effect of Insecticides on Secondary Pests, 1992

Experimental sprays were applied to single-tree plots in a randomized block design consisting of 2 replicates of ‘Golden Delicious’ and 2 replicates of ‘Yorking.’ Treated single trees were separated by others not sprayed with test insecticides. Trees were 8 years old and planted 20 x 30 ft apart. NTN-33893 and Carzol/Cygon were applied dilute to run-off with a pressure hand gun at approximately 4.1 gal per tree. The airblast treatment of NTN was applied with a Myers Mity Mist sprayer calibrated to deliver 75 gal/acre at 2.0 mph for a complete spray. The NTN 5% RTU treatment was applied with a paint brush to the trunk in a 10-12 inch band 12 inch above the ground. Application dates are listed in the table. All plots received a regular fungicide maintenance schedule of captan 50 W, Dithane M-45, Nova 40 WP and Topsin M 85DF. Effect of sprays on WALH was evaluated by counting nymphs/25 injured leaves/tree. Effectiveness on the aphid complex was evaluated by counting aphid-infested leaves/10 top terminals, and aphids/most infested leaf. Effectiveness of test chemicals on ERM was evaluated by counting mites several times during the season on samples of 25 random leaves/tree, 100 leaves/treatment. Effect of sprays on SP was evaluated by 3-min counts of adults and larvae around the periphery of test trees. STLM control was evaluated by a 5-min count of mines around the periphery of trees at the end of both 1st generation and 2nd generation adult emergence. Russet ratings are based on 30 ‘Golden Delicious’ apples/replicate, 60/treatment. Fruits were rated as 0 (no russet), 1 (raised lenticels), 2 (1-10% russeted surface), 3 (11-25% russeted surface), 4 (26-50% russeted surface), or 5 (>51% russeted surface). Possible ranges are 0-30 (none to raised lenticels), 31-60 (raised lenticels to 1-10% russeted surface), 61-90 (1-10% to 11-25% russeted surface, 91-120 (11-25% to 26-50% russeted surface), and 121-150 (26-50% to >51% russeted surface).