A simple bioassay method for international comparison of insecticide susceptibility of the fall armyworm, Spodoptera frugiperda (J.E. Smith)
Related Research Project
Transboundary pest management
Description
The fall armyworm (FAW), Spodoptera frugiperda, was a native pest in the Americas (Fig. 1). However, FAW has recently invaded Africa and Asia and is rapidly expanding its distribution. This insect is a polyphagous pest and prefers maize. Due to the frequent use of certain inexpensive and easily available insecticides, resistance development is a concern in Asia. Because of the long-distance migration ability of FAW, if a strain develops resistance to insecticides in one country, it is likely to spread rapidly to neighboring countries. Therefore, it is essential to conduct insecticide susceptibility monitoring using the same methods and share the results to manage insecticide resistance development. For this purpose, we developed a simple insecticide susceptibility testing method using relatively easily available materials to monitor the insecticide susceptibility of FAW in Southeast Asia, including developing regions.This method can easily evaluate insecticide susceptibility, in contrast to existing methods such as molecular biology techniques and topical application. It consisted of the following procedures: collecting test insects, rearing them with an artificial diet made from relatively easily available materials, and susceptibility testing (Fig. 2). The artificial diet was composed of three fractions (Table 1). By feeding this artificial diet, 1st instar larvae could be raised to pupae (Fig. 3). We conducted diet-overlay bioassays using the 3rd instar larvae within three generations after collection to assess susceptibility. We applied 200 µl of insecticide serially diluted to any multiple using distilled water to 5 ml of artificial feed. After drying, ten 3rd instar larvae were introduced, and the number of dead individuals was counted 72 hours later. From the results obtained, the LC50 value was calculated. We evaluated the susceptibility of the insecticides that are applied in Southeast Asian countries to several FAW populations collected in Thailand using the developed method. The results suggested that the susceptibility of several insecticides decreased over time (Table 2).
The developed method showed enough accuracy and can be used for international comparison to develop resistance management measures. In Thailand, the susceptibility of FAW to several insecticides has decreased. Therefore, there is an urgent need to develop alternative control methods against FAW. The survival rate of 1st and 2nd instar larvae when fed an artificial diet was lower than when fed fresh maize leaves. Thus, fresh leaves are suitable for feeding the young larvae if it is necessary to examine a lot of insecticides in the same period.
Figure, table
- Research project
- Program name
- Term of research
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FY2021-2023
- Responsible researcher
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Kobori Youichi ( Crop, Livestock and Environment Division )
Thirawut Supangkana ( Plant Protection Research and Development Office, Department of Agriculture, Thailand )
Sutjaritthammajariyangkun Woravit ( Plant Protection Research and Development Office, Department of Agriculture, Thailand )
Rukkasikorn Artit ( Plant Protection Research and Development Office, Department of Agriculture, Thailand )
Punyawattoe Pruetthichat ( Plant Protection Research and Development Office, Department of Agriculture, Thailand )
ORCID ID0000-0003-0283-9136Noonart Uraporn ( Plant Protection Research and Development Office, Department of Agriculture, Thailand )
- ほか
- Publication, etc.
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Thirawut et al. (2023) CABI Agriculture and Bioscience 4: 19.https://doi.org/10.1186/s43170-023-00160-8
- Japanese PDF
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2023_B06_ja.pdf617.79 KB
- English PDF
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2023_B06_en.pdf676.64 KB
＊ Affiliation at the time of implementation of the study.