Efficacy of Insecticides for Control of Thrips on Onions, 1992

Nine insecticides were tested for control of thrips on onions grown in a Bernow series fine, sandy loam soil at the Wes Watkins Agricultural Research & Extension Center in Lane, OK. Onions were direct seeded into beds spaced 6 ft apart on 12 Sep, 1991 and thinned to 3 inch intervals on 4 Mar, 1992. Plots measuring 4 rows by 12 ft (0.0066 acre) and 10 ft buffers within rows were arranged in a randomized complete block design with 3 replications. A bed planted to wheat and rye bordered each side of all plots to minimize drift. Populations were assessed by counting all thrips larvae and adults on 5 plants/plot on 5, 8 and 12 Jun. A single insecticide application was made on 5 Jun after pretreatment counts with a CO2-powered backpack sprayer equipped with 2 hollow cone TX-18 nozzles/row that delivered 45 gal/acre at 40 psi. Adult thrips collected 4 Jun from untreated plots were determined to be 86% Frankliniella fusca and 14% Frankliniella occidentalis. Data were transformed [log (x + 1)] and analyzed using analysis of variance (ANOVA, SAS 1988) and means were separated using Ryan’s Q test.