In 2007–2008, the “annual bluegrass weevil,” Listronotus maculicollis Kirby (Coleoptera: Curculionidae), a serious pest of Poa annua L. (Poales: Poaceae) on U.S. golf courses, was shown to be resistant to two pyrethroids, bifenthrin and lambda-cyhalothrin. In 2008, we showed that bifenthrin resistance was principally mediated by oxidase detoxification (cytochrome P450 [P450]). P450s can be inhibited by demethylation inhibitor fungicides and gibberellin inhibitor plant growth regulators, both of which are commonly used on golf courses. We tested these compounds for synergistic activity with bifenthin against a pyrethroid-resistant population of L. maculicollis. The LD50 value for bifenthrin was significantly reduced from 87 ng per insect (without synergists) to 9.6–40 ng per insect after exposure to the fungicides fenarimol, fenpropimorph, prochloraz, propiconazole, and pyrifenox and the plant growth regulators flurprimidol, paclobutrazol, and trinexapac-ethyl. Simulated field exposure with formulated products registered for use on turf revealed enhanced mortality when adult weevils were exposed to bifenthrin (25% mortality, presented alone) combined with field dosages of propiconizole, fenarimol, flurprimidol, or trinexapac-ethyl (range, 49–70% mortality).
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1 October 2010
Synergism between Deinethylation Inhibitor Fungicides or Gibberellin Inhibitor Plant Growth Regulators and Bifenthrin in a Pyrethroid-Resistant Population of Listronotus maculicollis (Coleoptera: Curculionidae)
D. Ramoutar,
R. S. Cowles,
E. Requintina,
S. R. Alm
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Journal of Economic Entomology
Vol. 103 • No. 5
October 2010
Vol. 103 • No. 5
October 2010
fungicide
Listronotus maculicollis
P450 resistance
Plant growth regulators
synergist