Losses caused by Trialeurodes vaporariorum (Homoptera: Aleyrodidae) and Thrips palmi (Thysanoptera: Thripidae) on snap beans in the Cauca Valley of Colombia

Abstract

Yield losses on snap beans caused by the Trialeurodes vaporariorum (Westwood) and Thrips palmi Karny complex were measured. Three experiments were conducted in the Pradera location of the Cauca Valley (Colombia) at an altitude of 980 m.a.s.l. and 23ºC. The first two trials had an experimental design of randomized complete blocks with four repetitions and six treatments. Treatments were differential chemical control regimes so that potential losses caused by thrips, by whiteflies, and by the complex could be measured. Residual and marginal losses were also measured. A 4 x 4 latin square design was used in a third trial in which an absolute check was compared with whitefly and thrips control, whitefly control, and thrips control. In the first two trials mean potential losses due to the whitefly-thrips complex were 44.5% (range: 39-53%); losses due to thrips averaged 28.4% (range: 25-35%); the whitefly caused average losses of 16% (range: 14-18%). In the third trial. losses caused by the whitefly-thrips complex, by thrips alone and by the whitefly alone averaged 47.4, 30.9, and 16.5%, respectively. Residual losses (those incurred by the farmer following his own methods of control) were 14% (range: 8-22%). Marginal losses (those occurring when an action threshold for whiteflies is used) averaged 27% (range: 23-33%).