Evaluation of three natural enemies : Phytoseiulus persimilis, Amblyseius swirskii, and Beauveria pseudobassiana, for the integrated management of greenhouse vegetable arthropod pests

Abstract

Biologically-based integrated pest management (IPM) has become one of the main pest control strategies on high-value agricultural crops. However, in Lebanon, most of the farmers rely on frequent application of pesticides due to lack of alternative and effective pest control approaches. For that reason, field studies were conducted to assess the control efficacy of Amblyseius swirskii and Phytoseiulus persimilis for the management of greenhouse cucumber arthropod pests. The laboratory study focused on the use of Beauveria pseudobassiana for the control of Tuta absoluta. To test the efficacy of the natural enemies, two greenhouses were selected at each of the two selected experimental sites. One greenhouse served as a control where the farmer followed his normal plant protection practices while in the other, IPM practices were implemented including natural enemy releases. The populations of insects and mites were recorded on cucumber leaves and-or flowers. In the IPM greenhouses, A. swirskii successfully maintained whitefly nymph and thrips populations below their economic threshold levels, during most of the growing period. Moreover, P. persimilis, applied at the proper time, was highly effective in reducing spider-mite infestations. In the control greenhouse, at site A (Tamich), whitefly populations were maintained at a very low level while thrips and mite populations exceeded the ETLs, despite of 8 insecticidal-acaricidal sprays. On the other hand, at site B (Zahrani), the farmer was able to supress all arthropod pest populations below the ETLs due to heavy pesticide applications, which totaled 15 sprays each consisting of mixtures of a minimum of three pesticides. To test the efficacy of B. pseudobassiana, different conidial suspensions, ammended with or without adjuvants, were sprayed on T. absoluta eggs placed on detached tomato leaves in Petri-dishes. The results showed that the entomopathogenic fungus was highly effective in controlling the egg and larval stages of T. absoluta, in a dose-dependant infecti