ONION THRIPS CONTROL IN ONION – TRIAL I, 2010

Abstract

Onion thrips: Thrips tabaci Lindeman Control of onion thrips was evaluated using foliar-applied insecticides in a commercial onion field near Potter, New York. Dry bulb onion seeds were planted in muck soil on 22 Apr 2010. 'Nicolet' is a yellow globe variety that matures about 112 days after emergence. Treatments were arranged in a RCB with four replications. Each plot was a single 20-ft long row flanked by untreated rows and rows were spaced apart by 38 cm. Foliar treatments were applied at 42 gpa and 40 psi using a CO 2-pressurized backpack sprayer equipped with a single, twin flat-fan nozzle (TJ60-8004VS). To improve penetrability of the insecticide into the leaves, most treatments included the non-ionic surfactant Induce at a rate of 0.5% vol/vol. Dyne-Amic at a rate of 0.25% vol/vol was added to Movento and no surfactant was added to Requiem because it already has a surfactant-like property in the formulation. Plots were initially sprayed on 23 Jun when plants had an average of 6.4 larvae per plant (1.3 larvae per leaf). Additional applications were made on 2, 8, 15, 22 and 30 Jul and 6 and 11 Aug. Conditions during this experiment were warmer than normal. Efficacy of treatments was evaluated by recording the number of larvae from 15 randomly selected plants per plot. Adults were not recorded because they often move between plots and their presence does not always reflect the efficacy of the treatment. Number of larvae per plot was recorded five to eight days after each application. Data were analyzed using ANOVA, with mean separation by Fisher's protected LSD at P<0.05. Thrips count data were transformed using a log 10 (x + 1) function before analysis, but untransformed means are presented. Onion thrips pressure was moderately high during this trial and peaked on 11 Aug. Movento, HGW86 10 OD and Radiant SC were the most effective products for controlling thrips larvae. The high and low rates of HGW86 provided a statistically similar level of thrips control, but numerically lower densities of thrips were more commonly observed in plots that received the high rate. Agri-Mek significantly reduced thrips densities relative to the untreated control, but did not perform as well as the products listed above. Lannate and Requiem did not control onion thrips.