Apple, Mite Control, 1985

Test chemicals were applied to 8- to 20-year-old apple trees at Monmouth, Maine, as dilute sprays using a hand gun and a hydraulic sprayer operating at 250 psi and at 300 (Test 3) to 350 gal/acre. Spray dates were 30 Apr (half-inch green, HIG), 11 May (tight cluster, TC), 16 May (pink, P), 24 May (bloom, B), 28-29 May (petal fall, PF), 7 Jun (first cover, IC), and 17 Jul and 25 Jul. The standard pesticide program consisted of Difolatan 4F (5 qt/100) on 24 Apr, Captan 80W (1 lb) on 5 dates, Cyprex 65W (0.8 lb) on 1 date, Imidan 50W (1.1 lb) on 1 date, Sevin 80W (1.25 lb) on 4 dates, and on 4 Jun there was a mixture of epsom salts (15 lb), Solubor 20W (1 lb), zinc chelate (1 lb) and Manzate 200 80W (1 lb). 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 3 ‘Red Delicious’ and 1 ‘Cortland’ cultivar in Test 1 and 2 ‘Red Delicious’ and 2 ‘Cortland’ cultivars in Tests 2 and 3. 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 and Jun were cool, the first half of Jul was wet (3.9 inches rain), and Aug was wetter (3.4 inches rain) and cooler than normal.