title: Enhanced esterase activity and resistance to azinphosmethyl in target and nontarget organisms.
abstract: The organophosphorous compound azinphosmethyl (AzMe) is applied extensively in northern Patagonia (southern Argentina) to manage codling moths (Cydia pomonella). This area is irrigated by fast-flowing channels that provide a favorable habitat for many species, including amphipods (Hyalella curvispina) and a field-mixed population of black flies (Simulium bonaerense, Simulium wolffhuegeli, and Simulium nigristrigatum). In the present study, AzMe susceptibility and carboxylesterase (CarbE) activity from both insecticide-exposed and nonexposed field populations were studied. The median lethal dose determined in codling moths from an insecticide-treated orchard was significantly higher (3.48 microg/insect) than that observed in those from an untreated orchard (0.69 microg/insect). Similarly, the median lethal concentration (LC50) determined in black flies collected from the treated area (0.021 mg/L) was significantly higher than that recorded in those from the untreated site (0.011 mg/L). For amphipods, both a subpopulation susceptible to AzMe (LC50, 1.83 microg/L) and a resistant one (LC50, 390 microg/L) were found in the treated area. Both subpopulations were more resistant to AzMe than the population from the untreated site (LC50, 0.43 microg/L). Significant differences (p < 0.001) in CarbE activities were observed between populations from pesticide-treated and untreated areas. Mean activities +/- standard deviation from treated and untreated sites were 0.21 +/- 0.16 and 0.016 +/- 0.008 micromol/min/mg protein, respectively, for codling moths; 2.17 +/- 1.71 and 0.81 +/- 0.35 micromol/min/mg protein, respectively, for black flies; and 0.27 +/- 0.10 and 0.14 +/- 0.07 micromol/min/mg protein, respectively, for amphipods. The results suggest that enhanced CarbE activity is one of the mechanisms that provide AzMe resistance in H. curvispina, Simulium spp., and C. pomonella populations from the insecticide-treated areas.
authors.affiliation: Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, Neuquén 8300, Argentina.
authors.forename: Olga L
authors.initials: OL
authors.lastname: Anguiano
authors.forename: Ana
authors.initials: A
authors.lastname: Ferrari
authors.forename: Ii Jimena
authors.initials: IJ
authors.lastname: Soleño
authors.forename: María C
authors.initials: MC
authors.lastname: Martínez
authors.forename: Andrés
authors.initials: A
authors.lastname: Venturino
authors.forename: Ana M
authors.initials: AM
authors.lastname: Pechen de D'Angelo
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Montagna
mesh_terms: D033304:Amphipoda; D000818:Animals; D001387:Azinphosmethyl / Q000633:toxicity*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000633:toxicity*; D004175:Diptera; D004351:Drug Resistance; D004950:Esterases / Q000378:metabolism*; D007306:Insecticides / Q000633:toxicity*; D007448:Invertebrates / Q000502:physiology*; D007814:Larva; D007928:Lethal Dose 50; D009036:Moths
chemical_list: D002800:Cholinesterase Inhibitors; D007306:Insecticides; D001387:Azinphosmethyl; D004950:Esterases; D002265:Carboxylic Ester Hydrolases