Gaucho as an Aphicide in Spring Barley

Abstract

Abstract Plots were seeded by small plot drill on 14 May (80 lb/acre) at the USDA-ARS Western Regional Plant Materials Introduction Center at Central Ferry, WA. Gaucho was applied as a seed treatment and Dimethoate was applied 20-days after emergence (DAE) with a CO2-powered backpack sprayer at 20 gpa and 20 psi, with the spray buffered to pH 5.0. Plots were 10 X 30 ft replicated 4 times in a RCB design. The experiment was designed to measure 1) the impact of Russian wheat aphid (and other cereal aphids present) on spring barley yields at economic injury levels; 2) the value of Gaucho as an aphicide in spring barley; and 3) effects of aphid controls on parasitoids of RWA and other species. Treatments were evaluated at 6, 13, 20, 27, 34, 41, 48, and 55-DAE by visual examination for each aphid species per tiller plus number of aphids per tiller, and the mean number of aphids parasitized (Diaeretiella rapae Hymenoptera: Aphidiidae in all cases). The dimethoate treatment was made on 20-DAE (approaching economic injury level) and evaluated on 6-DAT (27-DAE) and 13-DAT (34-DAE) as well as on all other DAE dates. At crop maturity, yield was calculated from m2 samples from each replicate to provide mean tons/acre for each treatment. Data were analyzed by ANOVA (P = 0.05; LSD).