Determination of the Persistence of Some Entomopathogenic Fungi and Wettable Powder Formulations on Concrete Surfaces against Major Stored Product Pests

In this study, the entomopathogenic fungi Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) and Metarhizium robertsii Sorokin (Hypocreales: Clavicipitaceae) and their wettable powder (WP) formulations were evaluated for efficacy and persistence on concrete surfaces against major stored-product insect pests. B. bassiana (5-4) and M. robertsii (S3) isolates and their formulations (WP1 and WP2) were tested after 0, 30, 60, and 90 days of surface exposure. Adults of Rhyzopertha dominica (F.,1792) (Coleoptera: Bostrichidae) and Sitophilus oryzae (L.,1763) (Coleoptera: Curculionidae) and third-instar larvae of Plodia interpunctella (Hübner, 1813) (Lepidoptera: Pyralidae) were exposed to treated surfaces at 9×1010 conidia/m² under controlled laboratory conditions (25±2 °C, 65±5% RH, darkness). Persistence generally declined with increasing exposure time; however, formulated products retained efficacy better than unformulated spores. WP1 and WP2 maintained significant mortality against P. interpunctella and R. dominica after 30 days, while WP1 remained effective for up to 60 days. Mortality of S. oryzae was low throughout the study and decreased markedly after 30 days. Overall, WP1 showed the highest efficacy and persistence, indicating the potential of fungal wettable powder formulations for long-term biological control of stored-product insect pests.