Entomopathogenic Fungus and Enhanced Diatomaceous Earth: The Sustainable Lethal Combination against Tribolium castaneum

This study determined the efficacy of the Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) alone or combined with the diatomaceous earth DEA (a mixture of DE + abamectin) against adults and larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). DEA was evaluated at 50 ppm while the fungi at 1.6 × 105, 1.6 × 106, and 1.6 × 107 conidia/kg wheat). Mortalities were assessed after 7 or 14 days of exposure, while progeny reduction in adults after 30, 60, 90, or 120 days. The radial fungus growth was significantly affected by the dose of DEA. Mortalities were higher in the combined treatments compared to the application of DEA or B. bassiana alone for both larvae and adults. Larvae were more susceptible than adults in all treatments and exposure intervals. Insect survival and progeny production were recorded for four months. Significantly fewer progeny was noted on wheat treated with DEA + B. bassiana treatments compared with control. The maximum number of mycosed cadavers and the rate of sporulation were observed at the lowest dose of B. bassiana alone, followed by the higher doses gradually. These findings indicate that the DEA + B. bassiana combinations can efficiently control T. castaneum, providing long-term protection of wheat.