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Enhancing Virulence of an Entomopathogenic Fungus Against the Diamondback Moth, Plutella xylostella (Lepidoptera: Plutellidae), Through Integrated Formulation Strategies Under Laboratory and Greenhouse Conditions
1
Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan
2
Department of Plant Medicine, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan
*
Author to whom correspondence should be addressed.
Insects 2026, 17(6), 622; https://doi.org/10.3390/insects17060622 (registering DOI)
Submission received: 20 April 2026
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Revised: 31 May 2026
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Accepted: 9 June 2026
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Published: 12 June 2026
(This article belongs to the Section Insect Pest and Vector Management)
Simple Summary
The diamondback moth is a serious pest of cruciferous crops and is difficult to control because of its rapid life cycle and resistance to chemical insecticides. This study evaluated different strategies to improve the efficacy of the entomopathogenic fungus Beauveria namnaoensis PM-02, including nanoparticle formulations, oil-based formulations, and combinations with insecticides. Copper and zinc nanoparticle synthesis was performed using fungal biomass extracts, with putative nanoparticle formation inferred from visual changes in the reaction mixtures. Mortality increased with increasing concentration across all treatments. The highest mortality (100%) was observed in the oil-formulated fungus combined with insecticide treatment, as well as in the insecticide-only treatment, while the lowest mortality (43.3%) occurred in the fungus-only treatment at the lowest concentration under laboratory conditions. Similar trends were observed under greenhouse conditions. Overall, the findings suggest that the biocontrol potential of fungal isolates can be significantly improved through suitable formulation strategies.
Abstract
Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is a major cruciferous crop pest worldwide with resistance to multiple insecticide classes, highlighting the need for sustainable alternatives. Entomopathogenic fungi (EPF) are promising biocontrol agents, but their efficacy is limited by slow pathogenicity, environmental sensitivity, and low persistence on insect cuticles. This study evaluated integrated formulation strategies to enhance the virulence of Beauveria namnaoensis PM-02 against P. xylostella under laboratory and greenhouse conditions. Putative copper and zinc nanoparticle preparations were generated using fungal biomass extracts, with nanoparticle formation inferred from visual changes in the reaction mixtures. Oil-emulsified fungal formulations and combinations with emamectin benzoate were also evaluated. Larval mortality increased significantly with concentration, indicating a clear dose-dependent response. The combined treatment of oil-emulsified fungus and emamectin benzoate, along with emamectin benzoate alone, resulted in the highest larval mortality (100%), whereas fungus alone caused the lowest mortality (43.3%). Lethal concentration (LC50) analysis indicated high toxicity of the combined treatment, while lethal time (LT50) values demonstrated more rapid mortality for emamectin benzoate (0.176 days) and the combined treatment (0.830 days) compared with fungus alone (6.25 days). Under greenhouse conditions, the combined treatment showed the highest efficacy, reducing larval survival to 30% and demonstrating enhanced insecticidal activity. Overall, integrated formulation strategies significantly improved fungal efficacy against P. xylostella.
Keywords:
entomopathogen; diamondback moth; insect mortality; formulation
