Indirect Pest Evaluation on Apple, 1997

Experimental sprays were applied to single-tree plots in a RCB design consisting of 4 replicates of ‘Yorking’. Treated single trees were separated by others not sprayed with insecticides. The trees were 9 year old and planted to a spacing of 20 X 30 ft. All treatments were applied with a Myers Mity Mist sprayer calibrated to deliver 100 gpa, driven at 2.4 mph. Dates of applications are given in the first table. All plots received a regular fungicide maintenance schedule of Benlate 50 DF, Dithane 75 DF, Nova 40 WP and Ziram 76 WP and the insecticide Imidan 70 WP. All maintenance materials were applied using the alternate row middle method of application. The effect of the sprays on WALH was evaluated by counting the number of nymphs/25 injured leaves/tree. Effectiveness on the spirea aphid was evaluated by counting the number of aphidinfested leaves/10 top terminals, and the number of aphids/most infested leaf, where a rating scale (0-4) was used instead of counting live aphids (see table footnotes for scale). The number of natural enemies of aphids was determined by counting the number observed on 10 growing shoots per tree. Effectiveness of the test chemicals on ERM was evaluated by counting the mites several times during the season on samples of 25 random leaves/tree, 100 leaves/treatment. STLM was evaluated by a 5-min count of tissue-feeding mines around the periphery of the trees at the end of the first and second generations. Also, the percentage stage distribution of sap-feeding and tissue-feeding mines of STLM was determined by randomly selecting 44 sap-feeding mines and observing their development every other day until all STLM eclosed as adults or the leafminer larva/pupa died. Pest pressure was moderate throughout the season.