Preparation, characterization, and insecticidal activity evaluation of three different formulations of Beauveria bassiana against Musca domestica

Abstract

Three formulations; bait, encapsulation, and emulsion of Beauveria bassiana were prepared and evaluated for their insecticidal activity in simulated field settings. Tea waste-based bait formulation of B. bassiana showed 100% mortality (within 72 h) in lab assay against adult houseflies. In field assay using traps, 65% relative entrapment and 100 % mortality (within 60 h) of entrapped flies was observed. Although the bait formulation was low cost and easy to prepare and transport, its storage ability was limited. Hence, more advanced formulations in form of encapsulation and emulsion was attempted. Encapsulated B. bassiana conidia (using skimmed milk powder, polyvinyl pyrrolidone K-90 and glucose as additives) showed 100% conidial germination and retained 78% conidial viability, even after storage for 12 months at 30 °C. Encapsulated product showed 54.8% (freshly prepared) and 30.6 % (after 12-months storage) mortality of housefly larvae in a simulated field condition. Emulsion formulation was prepared by using Tween 20 as surfactant with seven vegetable oils: soybean, rapeseed, sunflower, olive, castor, til, and linseed. Emulsion with linseed oil showing maximum conidial germination (94%) was evaluated for shelf life and pathogenecity against housefly larvae. Shelf life analysis of emulsion revealed 28% conidial germination and 19.9% housefly larval mortality after 12 months of storage as opposed to 94% conidial germination and 51.7% of larval mortality with fresh product. Significant increase in shelf × targeted application of formulation is expected to increase its mass applicability for housefly control. Also, the variability among products presents diverse opportunities for commercialization.