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Stage-Dependent Efficacy of Selected Biopesticides against Beet Armyworm, \textit{Spodoptera exigua} (Lepidoptera: Noctuidae), on Welsh Onion under Controlled Greenhouse Conditions

Loan Thi Thanh Nguyen1,2, Nguyen Thanh Thuy3, Ho Thi Thu Giang3, Than The Anh3
1Laboratory of Sustainable Development in Natural Resources and Environment, Institute for Advanced Study in Technology, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam
2Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam
3Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
DOI: https://doi.org/10.70517/revcc2624116
Published: 20/09/2026
: Loan Thi Thanh Nguyen, Nguyen Thanh Thuy, Ho Thi Thu Giang, Than The Anh. Stage-Dependent Efficacy of Selected Biopesticides against Beet Armyworm, \textit{Spodoptera exigua} (Lepidoptera: Noctuidae), on Welsh Onion under Controlled Greenhouse Conditions. Revista Cultura Científica, 2026 Issue 24. pg. 1414-1422.

Abstract

Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a major pest of Welsh onion, and effective biological alternatives to synthetic insecticides are increasingly needed for sustainable pest management. This study evaluated the efficacy of four commercially available biopesticides—Az Tron WG (Bacillus thuringiensis), HH-SK3 (Bacillus thuringiensis + Beauveria bassiana + Metarhizium anisopliae), Sokupi 0.5SL (matrine), and Meta Green (Metarhizium anisopliae)—against first- through fourth-instar S. exigua under controlled greenhouse conditions using a leaf-dip bioassay adapted from the IRAC susceptibility-test method for leaf-eating lepidopteran larvae. Corrected control efficacy was assessed at 24, 48, 72, 120, 168, and 336 hours after treatment (HAT), and treatment effects were analyzed using generalized linear mixed models. Control efficacy increased progressively with exposure time for all products, reaching 93.3–100.0% by 336 HAT across all larval instars. Younger larvae responded more rapidly than older larvae, with first- and second-instar larvae achieving \(\geq\)90% control by 120 HAT, whereas third- and fourth-instar larvae generally required 120–168 HAT to reach comparable efficacy. Az Tron WG consistently provided the fastest early suppression, although differences among products diminished with prolonged exposure. These findings indicate that all four commercial biopesticides are effective for managing S. exigua and emphasize that early application against young larval instars can accelerate control and strengthen integrated pest management in Welsh onion production.

Keywords: Spodoptera exigua, biopesticides, welsh onion, Matrine, Bacillus thuringiensis, Beauveria bassiana, Metarhizium anisopliae

Abstract

Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a major pest of Welsh onion, and effective biological alternatives to synthetic insecticides are increasingly needed for sustainable pest management. This study evaluated the efficacy of four commercially available biopesticides—Az Tron WG (Bacillus thuringiensis), HH-SK3 (Bacillus thuringiensis + Beauveria bassiana + Metarhizium anisopliae), Sokupi 0.5SL (matrine), and Meta Green (Metarhizium anisopliae)—against first- through fourth-instar S. exigua under controlled greenhouse conditions using a leaf-dip bioassay adapted from the IRAC susceptibility-test method for leaf-eating lepidopteran larvae. Corrected control efficacy was assessed at 24, 48, 72, 120, 168, and 336 hours after treatment (HAT), and treatment effects were analyzed using generalized linear mixed models. Control efficacy increased progressively with exposure time for all products, reaching 93.3–100.0% by 336 HAT across all larval instars. Younger larvae responded more rapidly than older larvae, with first- and second-instar larvae achieving \(\geq\)90% control by 120 HAT, whereas third- and fourth-instar larvae generally required 120–168 HAT to reach comparable efficacy. Az Tron WG consistently provided the fastest early suppression, although differences among products diminished with prolonged exposure. These findings indicate that all four commercial biopesticides are effective for managing S. exigua and emphasize that early application against young larval instars can accelerate control and strengthen integrated pest management in Welsh onion production.

Keywords: Spodoptera exigua, biopesticides, welsh onion, Matrine, Bacillus thuringiensis, Beauveria bassiana, Metarhizium anisopliae

References

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Loan Thi Thanh Nguyen
Laboratory of Sustainable Development in Natural Resources and Environment, Institute for Advanced Study in Technology, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam
Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam
Nguyen Thanh Thuy
Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
Ho Thi Thu Giang
Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
Than The Anh
Vietnam National University of Agriculture, Gia Lam, Hanoi, Vietnam
thantheanh@vnua.edu.vn

How to cite:

Loan Thi Thanh Nguyen, Nguyen Thanh Thuy, Ho Thi Thu Giang, Than The Anh. Stage-Dependent Efficacy of Selected Biopesticides against Beet Armyworm, \textit{Spodoptera exigua} (Lepidoptera: Noctuidae), on Welsh Onion under Controlled Greenhouse Conditions. Revista Cultura Científica, 2026 Issue 24. pg. 1414-1422.

Publication History

  • Received: 26/06/2026
  • Accepted: 11/09/2026
  • Published: 20/09/2026
Copyright © 2026, Loan Thi Thanh Nguyen, Nguyen Thanh Thuy, Ho Thi Thu Giang, Than The Anh. Published by Revista Cultura Científica. This article is published as open access under the Creative Commons Attribution 4.0 International (CC BY 4.0) license (http://creativecommons.org/licenses/by/4.0/).

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