Apple, Mite Control, 1984

Abstract

Abstract Test chemicals were applied to 7- to 23-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 to 400 (Test 2) gal/acre. Spray dates were 15 May (tight cluster), 3 Jun (petal fall), 13 Jun (first cover), and 6, 13, and 18 Jul. The standard pesticide program consisted of Difolatan 4F (5 qt/100 gal) on 29 Apr, Polyram SOW (1.8 lb) on 3 dates, Captan 80W (0.9 lb) plus Benlate 50W (2.9 oz) on 2 dates, Imidan 50W (1 lb) on 2 dates, and Sevin 80W (1 lb) on 3 dates. These 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’ cultivars in Test 1, 2 ‘Red Delicious’ and 2 ‘Cortland’ cultivars in Test 2, 4 ‘Cortland’ cultivars in Test 3, and 3 ‘McIntosh’ and 1 ‘Golden Delicious’ cultivars 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. Minimum temperatures of 36°-37°F were recorded on the 4 days following the tight cluster treatments, and maximum temperatures of89°-90°F occurred on the 2 days after the treatments on 13 Jul. Although the last half of Jun was wet (3.0 inches rain), Jul and Aug were dry (1.8 and 1.5 inches, respectively).