Apple, Summer Mite Control, 1979

Abstract

Abstract Test materials were applied to apple trees at MonmounS, Maine, as dilute sprays with a handgun from a hydraulic sprayer operating at 100 psi. In Test 1, 14-yr-old trees were sprayed at a rate of 600 gal/A; in Test 2, 18-yr-old trees were treated at 300 gal/A; and in Test 3, the rate was 200 gal/A for 23-yr-old trees. Spray dates were Jul 6 and 13 (Test 1), and Jul 20 and 27 (Tests 2 and 3); each material was applied on both dates for the respective tests. The fungicide and insecticide program (rates are per 100 gal) during rhe course of these acaricide tests consisted of captan 80W (1 to 1.25 lb) on 3 dates and imidan 50W (1 lb) on ca. Jul 18, 30 and Aug 15. There were no tank-mixtures of acaricides with other pesticides. There were 4 single-tree replications per treatmert. A randomized complete block design was utilized with 2 Golden Delicious and 2 Red Delicious cultivars per treatment in Test 1, 4 Golden Delicious per treatment in Test 2, and 4 Red Delicious per treatment in Test 3. From each tree 25 leaves were collected mostly at chest-height around the periphery of the tree, brought into the laboratory, and the mites brushed onto glass plates coated with a Tween 20-alcohol mixture; mites were counted the same day. Mite population pressure was heavy in Aug except in Test 3. On the prespray date, egg populations ranged from 40 to 50 eggs/leaf (Test 1) to 15 to 30 eggs/leaf (Tests 2 and 3). Jul and Aug were dry and hot months except for heavy rains on Jul 16, 17, and 26.