Residual Control Using Reduced Insecticide Rates for Melanoplus Spp. in Alfalfa, 1989

Plots (63.7 by 63.7 m; 0.4 ha) were established (16 Aug) with an untreated check, Asana and 3 rates of XLR Sevin arranged in checkerboard fashion, which allowed grasshopper immigration into treated plots from all 4 directions. Applications were made with a Broyhill sprayer delivering 10 gal/acre at 40 psi using Teejet 8002 nozzles. A randomized complete block design was used with 4 replications. Forty rings (0.1 m2) were placed in 4 parallel rows in the central portion of each plot. Grasshopper counts (0, 5, 12, 16 and 30 d postapplication) were subjected to Abbott's formula which weights the percent reduction accounting for decreases in grasshopper counts exhibited in untreated plots.