Entomopathogenic fungi as potential biocontrol agents against Callosobruchus maculatus (F.) and Callosobruchus chinensis L. (Coleoptera: Chrisomelidae: Bruchinae) on stored cowpea seeds

The insecticidal efficacy of four species of Trichoderma genius (T. harzianum, T. citrinoviride, T. viride and T. asperellum) and Metarhizium anisopliae was assessed against Callosobruchus maculatus and C. chinensis on cowpea seeds at concentrations of 2.0 x 10(6), 2.0 x 10(7), 2.0 x 10(8) and 2.0 x 10(9) conidia/kg. The adult mortality was counted 3 and 7 days after treatment while progeny and seed weight loss were recorded after 45 days. After 7 days, all fungal strains caused significant adult mortality of both insects particularly at 2.0 x 10(9) spores/kg. Metarhizium anisopliae and T. citrinoviride were the most effective fungi inducing 95 and 93.2% mortalities of C. chinensis at 2.0 x 10(9) spores/kg, respectively. Callosobruchus chinensis was slightly more susceptible to the fungal strains than C. maculatus. Furthermore, the fungal strains at the highest concentration caused a significant reduction in F-1 progeny of both insects. After 45 days, T. harzianum at 2.0 x 10(9) spores/kg showed the highest protection of cowpea seeds against C. chinensis with weight loss of 6.5%. These findings indicate that the five fungal strains could be implemented in integrated pest management programs of these insects.