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 2nd
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.