Investigating zeta-cypermethrin resistance stability in California Drosophila suzukii populations

Drosophila suzukii (Matsumura) causes serious damage to soft and stone fruit globally, resulting in substantial economic losses. Due to its unique ability to oviposit in and degrade ripe fruit, management programs rely primarily on insecticides to minimize pest pressure. While insecticide resistance has been reported in D. suzukii populations, the stability of this resistance remains unknown. We assessed resistance stability to the pyrethroid insecticide zeta-cypermethrin in a field-collected D. suzukii population under continuous laboratory selection pressure over multiple generations and after the selection pressure was removed. We further assessed resistance stability following a population bottleneck resulting from applications of a greater concentration of the insecticide following initial laboratory selection.

Following termination of continuous zeta-cypermethrin laboratory selection for 20 generations, the LC₅₀ of the field-collected D. suzukii population remained stable for an additional 16 generations. A second field-collected population initially selected in the laboratory then subjected to a greater insecticide concentration to create a population bottleneck then followed by continued zeta-cypermethrin exposure after a recovery period resulted in increased resistance as indicated by LC₅₀ values.

Field derived resistance to a commonly used pyrethroid insecticide in D. suzukii can persist post-selection and following a population bottleneck in a laboratory environment. These are the first studies to assess insecticide resistance stability in this economically important pest, and results warrant consideration for pest management programs. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.