Wednesday, 20 November 2002 - 1:12 PM
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This presentation is part of : Ten-Minute Papers, Section F. Crop Protection Entomology

Stability of insecticide resistance in the leafminer, Liriomyza trifolii

J. Scott Ferguson, Vero Beach Research Center, Syngenta Crop Protection, Vero Beach Research Center, 7145 58th Avenue, Vero Beach, FL

Three populations of the leafminer, Liriomyza trifolii (Burgess), were collected from commercial ornamental production greenhouses in the United States – two from California and one from Georgia – for susceptibility tests with the insecticides cyromazine (Citation), abamectin (Avid) and spinosad (Conserve). A leaf dip bioassay of leaves containing young (1-2 d old) larvae was used. Based on larval mortality, the three strains varied in both spectrum and level of resistance. CA-1, collected from Gerbera daisy, was moderately resistant to cyromazine (18-fold) and abamectin (22.5-fold) but highly resistant to spinosad (>188-fold). CA-2, collected from chrysanthemums, was not resistant to abamectin, had a low level of resistance to cyromazine (8.2-fold) but was extremely resistant to spinosad (1192-fold). GA-1, collected from chrysanthemums, had very low levels of resistance to cyromazine (5.5-fold) and spinosad (4.5-fold) but was moderately resistant to abamectin (30.3-fold). When reared in the absence of insecticide selection pressure, all three strains reverted to approximately the level of the reference strain. The CA-1 strain reverted in 9 generations to cyromazine and spinosad, however, the lowest level of abamectin resistance reverted to was 3.2-fold at F8. The CA-2 strain reverted in 5 generations to cyromazine and 4 generations to spinosad. GA-1 reverted in 5 generations to abamectin. Based on the results, it appears that resistance to these three insecticides is unstable, at least in the initial instance. Additionally, there was no cross-resistance among these three insecticides.

Species 1: Diptera Agromyzidae Liriomyza trifolii
Keywords: insecticide resistance, leafminers

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