Apple, P. Ulmi Summer Control, 1975

Abstract

Abstract Test materials were applied to apple trees at Monmouth, Maine, as dilute sprays with a hand gun from a hydraulic sprayer operating at 250-300 psi. In Test 1, 25-year-old trees were sprayed at a rate of 250 gallons per acre; in Tests 2 and 3, 10-year-old trees were treated at 500 gallons per acre. Spray dates were July 10 and 18 (Tests 1 and 2) and July 28 and August 5 (Test 3); each material was applied on both dates. The fungicide and insecticide program during the course of these acaricide tests consisted of captan 80W (1 lb), Thiodan 50W (0.5 lb) and lead arsenate (2 lb/100 gal) on July 17, and Thylate 65W (1 lb) and Sevin 80W (1.25 lb/100 gal) on July 30. There were no tank-mixtures of acaricides with other pesticides. There were 4 single-tree replications per treat-ment. A randomized complete block design was utilized with 1 Red Delicious (RD) and 3 Golden Delicious (GD) cultivars per treatment in Test I; 1 Cortland (C) and 3 RD per treatment in Test 2; and 1 Early Mcintosh, 1 RD, 1 GD, and 1 C 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 brushed onto glass plates coated with a Tween 20-alcohol mixture; mites were counted the same day. Mite population pressure was very severe. At the prespray date egg populations ranged from 20-35 eggs/leaf (Tests 1 and 2) or from 40-80 eggs/leaf (Test 3). Late July and August were hot and dry.