Application technology for whitefly control Trialeurodes vaporariorum (Westwood) in tomatoes greenhouses

Abstract

Around Salto city (Uruguay), there is an important greenhouse tomato culture area. Whitefly Trialeurodes vaporariorum (Westwood) has turned into the principal plague, in spite of the high number of treatments and insecticides used. The most disseminated application technology is hydraulic spraying, with average application rate at full crop development of 1300 l ha^-1. An essay was installed to evaluate control alternatives during six months involving 22 applications in a 1.540 m^-2 tomato greenhouse. Treatments evaluated were: high and medium volume hydraulic spraying (800 and 350 l ha^-1), knapsack pneumatic spraying (175 l ha^-1), pneumatic spraying with and without electrostatic charge (100 l ha^-1). The 100 l ha^-1 treatments were applied with a GPS5K sprayer (Electrostatic Spraying Systems Inc, Watkinsville, GA). The experimental design was a completely randomized block design with three replications. Analyzed variables were whitefly adults at top end, and nymphs per leaf at medium plant height. For all sampling dates, adult’s presence with high volume hydraulic and pneumatic spraying with electrostatic charge were 46 and 2 respectively. Similar results for nymph’s presence were obtained, 17 and 2 nymphs per leaf respectively. Treatments with pneumatic spraying were more effective than those with hydraulics. Pneumatic electrostatically charged spraying achieved the highest whitefly control, reaching excellent sanitary condition until end culture, followed by the uncharged pneumatic spraying both with 100 l ha^-1 application rate.