Insecticide Resistance in Field and Laboratory Strains of Western Flower Thrips (Thysanoptera: Thripidae)

Abstract

Western flower thrips, Frankliniella occidentalis (Pergande), from 5 commercial greenhouses were resistant to diazinon, methomyl, bendiocarb, and cypermetluin, except in 2 tests with bendiocarb. When compared with the UMC-A reference strain, resistance ratios from LC₉₀s (BR₉₀) at 24 h ranged from 10.4 to 98 for diazinon, 3.4 to 26 for methomyl, 0.9 to 11 for bendiocarb, and 18.3 to 273 for cypermethrin. We also did toxicity studies on 2 laboratory strains (UMC, KCM). Compared with the UMC-A strain, RR₉₀s indicated that UMC thrips were resistant to diazinon (14-fold), methomyl (3.6-fold), and cypermethrin (232-rold), but not to bendiocarb. The RR₉₀of KCM thrips reared under diazinon selection increased from 4.0 to 271 when compared with UMC-A thrips. During diazinon selection, cross resistance to bendiocarb was evident, with the RR₉₀increasing from 0.4 to 14. Cross-resistance to cypermethrin also was present at the LC₅₀ (3.9-fold), but not at the LC₉₀. When compared with UMC thrips, KCM thrips also were resistant to permethrin (RR₉₀ = 2.5), fenvalerate (RR₉₀ = 3.6), DDT (RR₉₀ = 6.0), and imidacloprid (RR₉₀ = 14), but not to amitraz. Piperonyl butoxide, but not S,S,S-tri-n-butyl phosphorotrithioate, synergized the toxicity of diazinon, bendiocarb, and fenvalerate to KCM thrips.

Frankliniella occidentalis, insecticide, resistance