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Bioassays for Monitoring Insecticide Resistance
Published on: December 30, 2010
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Bioassay method for assessing insecticide susceptibility in thrips
Luiz Francisco Warpechowski1, Daniela Neves Godoy1, Eduardo Argenta Steinhaus1
1Department of Plant Protection, Federal University of Santa Maria, Santa Maria, RS, Brazil.
Neotropical Entomology
|October 23, 2025
Summary
A new dip test bioassay using soybean leaf discs effectively evaluates thrips susceptibility to insecticides like acephate and spinetoram. This method offers a reliable alternative for assessing insecticide resistance in thrips (Thysanoptera: Thripidae).
Area of Science:
- Agricultural Entomology
- Pest Management
- Insecticide Resistance Studies
Background:
- Thrips (Thysanoptera: Thripidae) are significant agricultural pests causing crop damage globally.
- Chemical insecticides are primary control methods, but insecticide resistance in thrips necessitates reliable susceptibility testing.
- Existing methods like the IRAC Susceptibility Test Method 010 can be resource-intensive.
Purpose of the Study:
- To develop and validate a simple, reliable bioassay method using soybean leaf discs for assessing thrips susceptibility to insecticides.
- To compare the efficacy of the new dip test method with the established IRAC Method 010 for evaluating thrips (Caliothrips phaseoli) response to acephate and spinetoram.
Main Methods:
- A dip test bioassay was developed using soybean (Glycine max) leaf discs to evaluate thrips susceptibility.
- The susceptibility of Caliothrips phaseoli to acephate and spinetoram was assessed using the new method and compared to IRAC Susceptibility Test Method 010.
- Probit analysis was used to model concentration-mortality data and compare lethal concentrations (LCs) between methods.
Main Results:
- Both bioassay methods yielded concentration-dependent mortality data that fit the probit model.
- Acephate showed similar lethal concentrations (LCs) between the proposed soybean leaf disc method and the IRAC method.
- Spinetoram exhibited higher LCs with the proposed method, but both insecticides demonstrated high field-level efficacy (96.5-100% mortality) across both methods against Caliothrips phaseoli.
Conclusions:
- The developed soybean leaf disc dip test is a simple, reliable, and statistically robust alternative to the IRAC method for assessing thrips susceptibility to insecticides.
- Acephate and spinetoram are highly effective against Caliothrips phaseoli at field label doses.
- This new bioassay method can aid in monitoring and managing insecticide resistance in thrips populations, supporting sustainable agriculture.
