Apple, Mite Control, 1987

Abstract

Abstract Test chemicals were applied to 10- to 31-yr-old apple trees at Monmouth, Maine, as dilute sprays using a handgun and a hydraulic sprayer operating at 250 psi and at 325-350 (Tests 1 and 2) to 375-400 gal/acre. Spray dates were 16 May (full pink), 29 May (petal fall), 12- 17 Jun (first cover) and 16 Jul (third cover). The standard pesticide program consisted of Difolatan 80 Sprill (8 lb/100) on 16 Apr (the only cover pesticide applied in Test 4), Captan 80W (1 lb) on 6-9 dates, Manzate 200 80W (1.5 lb) and Sevin 80S (1-1.2 lb) on 2 dates, and Pydrin 2.4EC (2.7 oz) on 4 dates. There were no mixtures of acaricides with other pesticides. There were 4 single-tree replications for each treatment. A randomized complete block design was used, with 2 'Red Delicious' and 2 'Cortland' cultivars in Tests 1 and 3, 3 'Red Delicious' and 1 'Cortland' in Test 2, and 4 'Cortland' in Test 4. From each tree 25 leaves were collected at chest height around the periphery of the tree, brought into the laboratory, and brushed onto glass plates coated with a Tween 20 and alcohol mixture; mites were counted the same day. May, June, July, and August were generally warmer than normal; all except June were relatively dry. Of special note were 94°F maximum temperatures recorded 1 and 2 days after the petal fall spray (Test 2).