SUSCEPTIBILITY OF FOUR STORED-PRODUCT INSECT PESTS TO BEAUVERIA BASSIANA AND METARHIZIUM ANISOPLIAE STRAINS

Insect infestations are considered one of the major problems causing enormous economic losses in stored grains. Laboratory bioassays were performed to establish the mortality induced by the commercially available Beauveria bassiana strain ATCC74040 (formulated product: Naturalis (R)) and by Metarhizium anisopliae strain CIST8 against four stored products pests. Adults of four grain and legume pest species (Cathartus quadricollis, Callosobruchus maculatus, Sitophilus granarius, and Oryzaephilus surinamensis) were exposed in laboratory assays to three different concentrations (103, 105 and 107/mL) of each entomopathogenic fungal strain. For each insect species, fungal strain and concentration, the mortality was recorded daily over a period of 7 days. Mean survival time and final cumulative mortality were determined, and 7-day mortality curves were established. A significant effect of insect species, fungal strain, and conidial concentration was observed on the 7-day mortality curves and the final cumulative mortality. Also, the mean survival time varied significantly with the conidial concentration. In addition, a significant interaction between insect species and fungal strain was recorded for all three assessed parameters. In general, at all tested concentrations, B. bassiana strain ATCC 74040 caused higher mortality than M. anispliae strain CIST8 in all four insect species. Our results suggest that entomopathogenic fungi could be effectively used as part of an integrated pest management program for the control of legumes and grain pests.