Potato Insect Control, 1985

Abstract

Abstract Potatoes were planted on 9 May in So. Deerfield, MA. Fertilizer (700 lb 10N:10P2O5:10K2O/acre) was broadcast and incorporated prior to planting. An additional 700 lb/acre was sidedressed on 26 Jun. Soil type was a fine sandy loam with a pH of ca 5.3. The land was rotated from corn, and no other potato crops were planted within 0.5 miles; therefore, Colorado potato beetle (CPB) pressure was moderate. Treatment blocks were replicated 4 times in a randomized complete block design. Each plot consisted of 2 30-ft rows with a 3 ft fallow area separating each plot. Insecticides were applied with C02 pressurized sprayers at 40 psi, with a delivery rate of ca. 65 gal/acre. Applications were made on 3, 11, and 17 Jul. Temik 15G (3.0 lb (AI)/acre) was applied at planting, and Temik 15G (2.0 lb (AI)/acre) at plant emergence. For this reason, the pre-counts (3 Jul) for these two treatments were significantly lower than all the other treatments. Because Kryocide 8F was not available for the first generation applications, a separate trial, adjacent to the trial area at a location where first generation CPB larval counts were still high, was carried out on 18 Jul (Kryocide 8F and control). The mean number of larvae per ten stalks before treatment was 83.4 for the control and 88.8 for the Kryocide 8F plots. After treatment (22 Jul), the control had 94.5 larvae/10 stalks; the Kryocide treatment had 14.3 larvae/10 stalks. CPB densities were determined on 3 Jul (before treatment) and 4-5 days after treatment by counting adults and larvae on 10 primary stalks in each plot. Green peach aphids (GPA) were sampled on 29 Jul by counting those found on 10 terminal leaflets from lower leaves. Predators were assessed on 29 Jul by counting individual larvae, pupae and adults per 10 stalks. Coleomegilla maculata was the dominant predator species. Because densities of individual species were not high, predator numbers were pooled. Each plot was rated for defoliation on a scale from 1 (0-20%) to 5 (80-100%). Potato leafhopper (PLH) damage was assessed by ranking damage from 1 (no damage) to 3 (severe).