Survival of Indian Honey Bee Apis Cerana indica Fabricius exposed to Microbial Control Agents: Insights into Its Pathogenicity and Toxicity under Varied Exposure Methods

This study investigates the effects of commercially available entomopathogenic fungal formulations on the Indian honey bee Apis cerana indica Fabricius (Hymenoptera: Apidae). A 10-day bioassay conducted under laboratory conditions used four methods (topical, spray, leaf dip, feeding) to evaluate the pathogenicity of Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), Beauveria brongniartii (Sacc.) Petch (Hypocreales: Cordycipitaceae), Metarhizium sp. (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae), and Lecanicillium sp. (Zimmermann) Zare & Gams (Hypocreales: Cordycipitaceae) on A. cerana indica at 5 × 108 conidia/ml. After exposure to fungal formulations via different methods, we recorded conidial acquisition by bees (4.36 × 104 – 21.08 × 104 conidia/bee). The mortality rates were significantly lower in the topical (6.58%), leaf dip (10.17%), spray (9.92%), and feeding (9.17%) exposure methods, indicating their nontoxicity (< 25% mortality) according to IOBC classification. Among the fungal formulations tested, Lecanicillium (93.25%) recorded significantly higher survival rates. Mycosis percentage (3.66 – 15%) was observed in the 10-day-old moribund bees. The lethal time (LT) estimates, viz., LT10 and LT25, were comparatively lower in the topical exposure method (LT10: 13.4 – 16.08 days, LT25: 17.08 – 19.68 days). However, the effects of entomopathogenic fungal formulations must be further confirmed under field conditions.