Certain entomopathogenic fungi, such as Beauveria bassiana, are highly pathogenic to arthropod pests and are able to colonize plant tissues, thereby enhancing both plant growth and disease resistance. This study assessed three B. bassiana strains (CBM1, CBM2, and CBM3) for their pathogenicity toward insect larvae and colonization potential in wheat. The insecticidal activity of the fungi against the larvae of the major lepidopteran pests Helicoverpa armigera, Spodoptera frugiperda, Mythimna separata, and Plutella xylostella was determined. The fungi were then applied to wheat plants using seed immersion and soil drench methods; their colonization rates were compared, and the impacts of fungal colonization on wheat growth and survival were evaluated. The results demonstrated that all three strains were effective in reducing insect damage, with B. bassiana CBM1 exhibiting the highest pathogenicity followed by CBM3 and CBM2. B. bassiana CBM1 was particularly effective, with a significantly higher colonization rate achieved through soil drenching compared to seed immersion. The soil inoculation of B. bassiana resulted in increased plant height at 30 days after sowing (DAS) and root length at 15 DAS compared to the control group. B. bassiana CBM1-colonized wheat increased the mortality of fall armyworm. This research has enriched the biological control microbial resource pool and highlights the potential of B. bassiana in integrated pest management strategies.

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 aimed 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 x 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 x 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 with 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 while overcoming current resistance issues. The JEF-507 isolate has been registered in Korea, 2022 and successfully commercialised as the name of Chongchae-Stop in this local market to control whitefly and thrips.

Insect pests are serious threats to agriculture, forestry, and human health because they damage crops and trees and spread diseases. Chemical insecticides control insect pests quickly and effectively, protecting crops. Environmental and health concerns arise from their use. Long-term exposure can cause pesticide-resistant insects, requiring stronger chemicals. Beneficial insects and wildlife may be harmed. Some chemical insecticides persist in the environment, causing long-term ecological damage. The present study was to isolate, identify, and characterize entomopathogenic fungi from the soil, evaluate their pathogenicity against major insect species, and evaluate the non-target effect on soil bioindicator species. Bioassay results show that Beauveria bassiana conidia are more pathogenic to all three species at 10 days after treatment, causing 100% mortality in Halyomorpha halys and Tenebrio molitor within 10 days. The lethal concentration showed lower LC50 values of 9.5 x 103 conidia/mL in H. halys, 2.6 x 103 conidia/mL in T. molitor, and 8.3x104 conidia/mL in P. japonica, B. bassiana treatment results showed a shortened insect life time LT50 of H. halys (6.0 days), T. molitor (5.3 days), and P. japonica (6.9 days). The present study concluded that B. bassiana fungi conidia are more efficient against three major insect pests.

Fall armyworm, Spodoptera frugiperda is an invasive polyphagous pest and has annually invaded Korea since it was first reported in 2019. This pest has already acquired resistance to synthetic chemical pesticides. To minimize the damage caused by S. frugiperda, alternative control methods with different mode of action should be developed. In this study, we assessed the virulence of native entomopathogenic fungi against S. frugiperda and investigated application methods to effectively control the target insect. We obtained 93 fungal isolates and assayed their pathogenicity against second instar larvae. Of the 93 isolates, 34 isolates caused high mortality. Based on their virulence, conidial productivity, and thermotolerance, ten isolates were selected for quantitative bioassays. In the bioassays using leaf dipping, all isolate treatments showed high virulence against second instar larvae, but only two isolates, Beauveria bassiana JEF-492 and Sf83 caused 93.3% and 86.7% mortality against fourth instar larvae, respectively. Given the soil-dwelling pupal stage, drenching the soil with Metarhizium anisopliae JEF-157 and B. bassiana JEF-492 from the selected isolates reduced the survival rate of pupae by up to 80% under laboratory conditions. The M. anisopliae JEF-157 and B. bassiana JEF-492 cultured on barley and rice showed high conidial productivity and thermotolerance. Our results show that soil application of M. anisopliae JEF-157 and B. bassiana JEF-492 targeting pupal stage could be effectively combined with the spray on the leaf-dwelling larval stage when the isolates encounter unfavorable abiotic stress on the leaves.