Potential of the entomopathogenic fungus, Metarhizium anisopliae (Metsch.) Sorokin for control of the legume flower thrips, Megalurothrips sjostedti (Trybom) on cowpea in Kenya

Field experiments were conducted at Mbita, western Kenya for two seasons to evaluate the potential of the entomopathogenic fungus, Metarhizium anisopliae (Metsh.) Sorokin, for biological control of the legume flower thrips, Megalurothrips sjostedti (Trybom), on cowpea. An ultra-low-Volume (ULV) oil/aqueous formulation and a high-volume (HV) aqueous formulation of conidia were applied three times each at two concentrations of 1 x 10(11) and 1 x 10(13) conidia ha(-1). Compared with the untreated controls, both formulations significantly reduced thrips populations and plant damage in both seasons. Adult insects collected from fungal-treated plots and reared in the laboratory showed a high mortality due to mycosis. Flower and pod production was significantly higher in treated plots compared to the control plots. HV formulation was superior to ULV formulation in reducing thrips population and plant damage, and in increasing flower and pod production. During the first season, plots treated with KV formulation at 1 x 10(13) conidia ha(-1) produced yields that were significantly higher than other treatments. No significant difference in grain yield was found between the fungal-treated plots and the synthetic insecticidal treatment during the second season. The results of these experiments suggest that M. anisopliae is a potential candidate for the management of M. sjostedti on cowpea. (C) 1998 Elsevier Science Ltd. All rights reserved.