The thrips Frankliniella occidentalis causes significant losses in areas of lettuce production, damaging leaf tissue during feeding and vectoring pathogenic viruses. The development of new strategies for the control of thrips in greenhouses is essential to reduce problems caused by the constant use of chemical insecticides. The efficiency of applications of Metarhizium anisopliae (strain 1104), at the concentrations of 5x10(6) and 1x10(8) conidia ml-1, was evaluated for the control of thrips in areas of hidroponic lettuce production. The number of adults per plant was observed, in comparison to initial infestation. The application of the fungus, in both concentrations, caused a 60% reduction of the thrips population, 6 days after the first application. In areas that did not receive the treatment with the fungus, the thrips population increased by 46.5%. However, the number of adults captured in sticky traps was similar for treated and non-treated areas, suggesting a high mobility of thrips adults in the greenhouse. A high number of dead adults with fungal structures was also observed in the areas treated with M. anisopliae. The apparent health and environmental safety of this entomopathogenic fungus makes this microorganism a promising alternative for chemical insecticides in lettuce production. More detailed studies about the interaction of this thrips and the use of M. anisopliae under greenhouse conditions are necessary to make applications in large scale viable.
fungus; thrips; microbial control