Evaluación Del Hongo Verticillium Lecanii En El Control de la Mosca Blanca, Trialeurodes Vaporariorum En Frijol

Abstract

The fungus Verticillium lecanii (Zimm) Viégas is a parasite of several insect species belonging to the order Homoptera, Coleoptera and Lepidoptera. It has a cosmopolitan distribution and currently there are commercial formulations for aphids and whitefly control. In Colombia there have been natural epizootics of the fungus of Trialeurodes vaporariorum (Westwood) in bean crops at Rionegro, Antioquia. The objectives of this research were to compare growth at different temperatures, development in different culture media and pathogenicity against adults of T. vaporariorum , of a a local isolate (VL-MB) and a comm.ercial formulation (Vertalec) of the fungus. The pathogenicity test was conducted using three concentrations (10 4 , 10 6 , 10 8 conidial/ml), which were sprayed on bean plants previously infested with adult whiteflies. The plants were seeded in pots and maintained isolated in screen cages placed in a field house exposed under enviromental conditions (15.5°C and 92% RH). Results indicated that growth of both isolates was best at 25°C and reduced at lower or higher temperatures. The most suitable media for both isolates were Sabouraud-dextrose-agar and Sabouraud-maltose-agar plus yeast extract. A regression analysis showed a linear trend (P>0.01) of fungal growth in all the cases and can be predicted by the equations obtained. The pathogenicity test showed that concentrations of 10 8 conidia/ml of VL-MB caused 72% mortality in adults of T. vaporariorum . The commercial isolate was not pathogenic to the whitefly. The fungicides tested in vitro against V. lecanii , using 1/10 of the commercial rate, did not inhibit significantly the local isolate (VL-MB) development. The least toxic fungicide was cupric oxychloride followend by Maneb, Benomyl and Chlorothalonil.