Apple, Full Season Insecticide Evaluations, 1981

Abstract Experimental insecticide treatments were applied in a comparative test to mature semi-dwarf Golden Delicious trees on May 13, May 27, Jun 11, Jun 25, Jul 9, Jul 23, Aug 11 and Sep 2-3. Treatments were applied with a Bean 35 gal/mln (132.49 litres/min) hydraulic sprayer operating at 300 psi (21.09 Kg/cm ). Single tree treatments were replicated four times in a randomized block design. Trees were sprayed to run-off. Mites were counted on 25 leaves from each tree using a modified Henderson-McBurnie leaf brushing technique. In the Aug 5 evaluation, twospotted spider mites were recorded separately. Counts of S. punctum adults and larva, Chrysopa spp. larva, O. insidiosus, L. mali and spiders were made on Aug 7 and Aug 14. Five limbs on each tree were tapped over a one square meter sheet of white cloth by striking each limb 5 times with a rod. Predators dislodged onto the sheet were recorded. Significant differences (P = .01) were observed between treatment means for all predators except L. mali and spiders. The Aug 7 count indicates the seasonal buildup of these predators after 6 pesticide applications. The Aug 14 evaluation more accurately represents the immediate effects of the Aug 11 application of the test materials. These data must be considered in conjunction with the mite data since in some cases (particularly the DPX-3792 treatment) mite populations were controlled and therefore predator populations never materialized. Rosey apple aphid damage was evaluated on Aug 13 by counting all damaged fruit clusters that could be found in a two minute search on the tree from the trunk to the outer perimeter of the canopy and to a height of 10 feet above the ground. A damaged fruit cluster consisted of 1 or more apples on a fruiting spur which had been damaged by rosy apple aphid feeding. Fruit was harvested (100 apples/rep; 400/treatment) and evaluated in mid-Oct for the leafroller complex (VL, TABM, RBLR), codling moth, curculion, scale and tarnished plant bug. Of these pests, only the leafroller complex was present in sufficient numbers to show significant differences (P = .01) between treatment means. Samples were evaluated for finish differences on a scale of 0 to 6 (0 = no russet, 6 = severe russet). Fruit size and weight measurements were recorded but no significant differences were found (P = .01) between treatment means or treatments and check.