Green Peach Aphid and Peach Twig Borer Control, Pre-Bloom Applications, 1984

Abstract

Abstract Insecticides were evaluated for control of the green peach aphid and peach twig borer at 4 locations near Wenatchee. Treatments were applied with a handgun sprayer at 400 psi to the point of drip simulating a dilute application of approximately 400 gal per acre. Peach varieties in test 2 were Elberta and Early Red Haven, in test 1 mixed, in test 4 Elberta and JH Hale. Nectarine varieties used in test 3 were Nectared and Ruby Grand. In tests 1-3, four single-tree replicates were used per treatment in a randomized complete block design. In test 4, unreplicated blocks of 16 trees were used per treatment. Pretreatment samples consisted of 5 twigs per tree in tests 1-3 and 5 twigs per tree from 8 trees in test 4. All aphids on each twig were counted. Posttreatment samples consisted of counting the number of aphids on each of 5 twigs per tree, the number of active green peach aphid colonies per tree and the number of growing shoots flagged by peach twig borer larvae. In tests 1 and 2, the first 3 treatments (Thiodan, Orthene and methomyl) were applied on 15 Mar before rain began. Subsequent applications were discontinued on that day. On 19 Mar all treatments in test 1, 2 and 4 were applied, including retreatment of the first 3 treatments listed in tests 1 and 2. Flower buds were swollen with some pink showing at this application. A heavy rain fell on the evening of 19 Mar extending through 21 Mar (0.95 inches). All applications had dried on trees prior to the beginning of the 19 Mar rain. On 23 Mar, treatments were applied in test 3. Fruit buds had advanced to the full pink stage with a few flowers open on some trees. Low to moderate populations of aphids were present in all test orchards. Mites were sampled on 2 Jul and 30 Aug from tests 2, 3 and 4. Fifty-leaf samples (5 leaves from 10 trees) were collected at each date from each treatment in test 4. A 25-leaf sample was collected from each tree in tests 2 and 3 on each sample date. Leaf samples were brushed and mites counted in the laboratory. Data are presented as the average number of mites per leaf for the 2 samples.