Monitoring of Spotted-Wing Drosophila (Diptera: Drosophilidae) Resistance Status Using a RAPID Method for Assessing...

Area of Science:

• Agricultural Entomology
• Pest Management
• Insecticide Resistance

Background:

• The invasive fruit fly, Drosophila suzukii, poses a significant threat to berry and cherry production.
• Insecticides are crucial for managing D. suzukii during fruit ripening and harvest.
• Monitoring insecticide resistance is vital for effective pest control strategies.

Purpose of the Study:

• To field-test the Rapid Assessment Protocol for IDentification of resistance in D. suzukii (RAPID) for identifying insecticide resistance.
• To evaluate the effectiveness of RAPID across multiple U.S. states and insecticide classes.
• To determine the prevalence of insecticide resistance in D. suzukii populations.

Main Methods:

• Field-testing RAPID on 78 D. suzukii populations across eight U.S. states in 2017-2018.
• Exposing flies to varying concentrations (LC50, LC99x2, LC90x8) of malathion, methomyl, spinetoram, spinosad, and zeta-cypermethrin.
• Analyzing fly mortality rates and identifying populations with low mortality for further bioassays.

Main Results:

• High overall susceptibility to tested insecticides was observed, with average female mortalities of 93.3% (2017) and 98.5% (2018) at discriminating concentrations.
• RAPID identified populations with low mortality to spinosad, leading to the discovery of resistant populations in California berry crops.
• Adjusting discriminating doses improved the assay's accuracy, reducing instances of unexpected fly survival.

Conclusions:

• RAPID is a quick, low-cost method for identifying D. suzukii populations that require further resistance testing.
• Most U.S. fruit production regions maintain susceptibility to key insecticide classes.
• The protocol aids in targeted pest management and preserves the efficacy of essential insecticides.