Azinphos-methyl and carbaryl resistance in adults of the codling moth (Cydia pomonella (L.), Lepidoptera: Tortricidae) from Northeastern Spain

The resistance of Cydia pomonella (L.) to organophosphates is widespread throughout the pome fruit growing areas. The lethal effects of two insecticides inhibitors of the acetylcholine esterase, azinphos-methyl and carbaryl, were evaluated in adults of five and four field populations of the codling moth, respectively. The lethal concentrations (LC50 and LC90) of these insecticides were determined in a susceptible strain from Spain (S_Spain). Topical bioassays using the approximate LC90 values (3000 mg (a.i.)/L of carbaryl and 2000 mg (a.i.)/L of azinphos-methyl) that were obtained in S_Spain were tested as diagnostic concentrations. The enzymatic activities of mixed-function oxidases (MFO), glutathione S-transferases (GST) and esterases (EST) were measured to investigate their potential role in the detoxification of these insecticides.Carbaryl and azinphos-methyl caused ⩽53% and ⩽39% corrected mortality, respectively, in field populations, although the diagnostic concentrations applied were twofold and fourfold higher than the maximum concentration registered in Spain, respectively. The activities of MFO and GST were 7.3- to 16.1-fold higher and 2.5- to 3.7-fold higher in all the field populations compared to those in S_Spain, respectively.

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► Reduced susceptibility to carbaryl and azinphos-methyl on adults field populations of codling moth in Spain.
► The main metabolic resistance mechanism involved were the mixed-function oxidases, followed by glutathione S-transferases.
► The presence of a Pattern I AChE mutation type in Spanish field populations has not been confirmed.