Early-Season Evaluation of Insecticides on Apple, 1997

Seven insecticide treatments and a control, each replicated 5 times among ‘Golden Delicious’ and ‘Yorking’ trees, were applied to single-tree plots in a RCB design. The trees were planted at a spacing of 20 X 20 ft and were 24 years old. Experimental sprays were applied with a Myers Mity Mist airblast sprayer calibrated to deliver 100 gpa at 2.4 mph. The application dates of the various treatments were based on various phenological stages of ‘Golden Delicious’ development (see the first table for application dates). A regular fungicide schedule (Dithane 75 DF, Nova 40 WP, Ziram 76 WP) was maintained throughout the season. Post-bloom insecticides (Guthion 50 WP and Imidan 70 WP) were applied at 1- to 2-week intervals beginning at petal-fall in early May. Effectiveness of the sprays for rosy apple aphid control was evaluated by counting the total number of RAA injured clusters/tree in a 3-5- and 10-minute sample per tree on 15 May, 12 Jun, and 14 Jul, respectively. The number of RAA injured fruit per tree was determined by making a 10-min count on 14 Jul. STLM was evaluated on 6 and 16 Jun by counting the number of tissue-feeding mines per 5 minutes around the periphery of the tree. The number of motile ERM was determined by collecting 25 leaves per tree and brushing those leaves with a leaf-brushing machine. Pest pressure was moderate.