Soil Treatments with Systemic Insecticides for Control of Green Peach Aphids and Colorado Potato Beetles, Test 5, 1979

Abstract

Abstract On Apr 4 'Russet Burbank' potato seed pieces were planted in Ritzville silt loam soil (Mesic Colciorthidic Haploxerolls) with a pH of 6.2 and 1.6% organic matter at Yakima, WA. Granular insecticides were applied by 3 methods: 1) in the furrow over the seed piece at planting time (PT); 2) as post-emergence sidedress (SD); and 3) as post-emerge nee topical dressing (Top). In the PT method the seed pieces were planted on Apr 4 in open furrows and the granular insecticide were dribbled through a hand-held funnel-type applicator into the furrow over the potato seed pieces and covered with soil. In the SD method, in another set of plots, the plants were sided re ssed when about 75% had emerged (May 14). The granules were placed in 1-inch (2.5 cm) bands, 4 inch (10.0 cm) to each side and about the same depth as the potato seed pieces by using chisel shanks fed by Gandy applicators mounted on a tractor. In the Top method, on the same day in another set of plots, the discharge tubes on the Gandies were removed from the chisel shanks and the granules were spread over the tops of the small potato plants in a 10-12 inch (25.4 to 30.5) wide band. Then the granules were mixed with the soil and the plants were almost covered with soil using a Lilliston cultivator. All plots were 2-rows wide (5.6 ft or 1.7 m) and 33-ft (10.1 m) long. Each treatment was replicated 3 times in a randomized complete block design. The crop was sprinkler irrigated. On May 22 (48 days after PT and 8 days after SD and Top), 3 whole plants/plot were examined and the numbers of green peach aphids (GPA) and Colorado potato beetle (CPB) eggs were counted. The amount of CPB feeding damage in each plot was rated numerically from 0 to 5 (0 = no feeding and 5 = severe feeding). Twenty compound potato leaves were collected from each plot on Jun 7 and 19 and Jul 17. The number of GPA and CPB eggs on the leaves and the number of leaves showing CPB feeding damage were counted. The data were subjected to analysis of variance using Duncan's MRT.