Conidia productivity and whitefly insecticidal activity of Beauveria bassiana JEF-507

Silverleaf whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is a destructive insect pest damaging to diverse crops by vectoring several plant pathogenic viruses, which consequently causes economic losses in crop production. As the resistance of whiteflies to chemical insecticides is increasing, this study aims to investigate the potential of entomopathogenic fungi as an alternative. A total of 72 entomopathogenic fungal isolates, collected from soils using Tenebrio molitor larvae as an insect baiting method, were assessed for their virulence against 2^nd nymphs of whitefly. Their virulence was assayed by dipping whitefly-infested tomato leaves in fungal conidia suspensions at 1.0 × 10⁷ conidia/ml. Among the tested isolates, two isolates of Beauveria bassiana JEF-462 and JEF-507 showed high virulence. In the assessment of virulence depending on conidia concentrations, the estimated LC₅₀ values for JEF-462 and JEF-507 were similarly 8.7~14.0 × 10⁷ conidia/ml. However, B. bassiana JEF-507 showed higher conidial productivity and thermotolerance on most of tested 12 grain substrates than B. bassiana JEF-462, and millet was the most suitable grain substrate. Additionally, siloxane as a surfactant was able to sufficiently exhibit the insecticidal activity of JEF-507 against whitefly nymphs compared to other surfactants. In a pot-based greenhouse trial, JEF-507 showed higher control efficacy than chemical insecticides, dinotefuran and spinetoram. This work suggests that B. bassiana JEF-507 could be competitively used as a biopesticide to control silverleaf whiteflies whilst overcoming current resistance issues. The JEF-507 isolate has been registered in Korea, 2022 and successfully commercialized as the name of Chongchae-Stop^® in this local market to control whitefly and thrips.