Apple, Summer Mite Control, 1978

Abstract

Abstract Test materials were applied to apple trees at Monomouth, Maine, as dilute sprays with a hand gun from a hydraulic sprayer operating at 300 psi. In Test 1, 28-yr-old trees were sprayed at a rate of ca. 250 gal/acre; in Tests 2 and 3, 13-yr-old apple trees were treated at 500 to 600 gal/acre. Spray dates were Jun 23 and Jul 3 (Test 1), Jun 26 and Jul 3 (Test 2), and Jul 20 and Aug 16 (Test 3); each material was applied on both dates for the respective tests. The fungicide and insecticide program during the course of these acaricide tests consisted of captan 80W (1.25 lb/100 ga I) on 4 dates; Imidan 50W (1.25 lb/100 gal) on Jul 5, 17, and Aug 2; Thiodan 50W (.5 lb/100 gal) on Jul 11 and 17; and Sevin 80W (1.25 lb/100 gal) on August 15. There were no tank-mixtures of acaricides with other pesticides. There were 4 single-tree replications per treatment. A randomized, complete-block design was utilized with 2 Golden Delicious and 2 Red Delicious cultivars per treatment in Tests 1 and 3 and 2 Cortland and 2 Mcintosh per treatment in Test 2. 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 heavy in August. On the prespray date, egg populations ranged from 4 to 8 eggs/leaf (Test 1), 1 to 2 eggs/leaf (Test 2), or 15 to 30 eggs/leaf (Test 3). July and August were very dry and hot months.