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Codling moth, Cydia pomonella (L.) is a key pest of global importance that affects apple fruit production and whose populations have developed resistance to insecticides in many apple production areas. In Spain, enhanced cytochrome P450 polysubstrate monooxygenase (PSMO) activity is the main mechanism involved in insecticide detoxification by codling moth, although acetylcholinesterase (AChE) target site mutations have been described in two populations. However, the extent of AChE and knockdown resistance (kdr) mutations in Spain is unknown. To assess the actual occurrence of AChE and kdr mutations concurrently with the frequency of moths with PSMO enhanced activity (R-PSMO), 32 Spanish field populations from four apple-growing areas of Spain and two susceptible laboratory strains were evaluated. R-PSMO was significantly higher in 23 chemically treated field populations from Extremadura, Catalonia and Aragon, with proportions that varied between 25% and 90%, but no significant differences among strains and the non-chemically treated orchards (organic or abandoned) were observed. The AChE mutation (F290V) was detected in all field populations from Catalonia (n=21) and in three field populations from Aragon (n=5), with resistant phenotype proportions varying from 34.2% to 97.5% and from 7.2% to 65% in Catalonia and Aragon, respectively. In addition, the kdr mutation (L1014F) was detected in twelve Catalonian field populations, at rates of incidence ranging between 2.6% and 56.8%. A positive correlation between R-PSMO and AChE mutation was found. The origin of the mutations and their ability to persist and spread in field populations with different management systems is discussed.
The authors thank the fruit growers and pest control advisors of the different Spanish apple-growing areas for their help in accessing and identifying apple orchards and Mónica Pérez for her technical help. This work was funded by grant Fondo de Desarrollo Científico y Tecnológico, FONDECYT 11130599 (CONICYT), Chile, to M.A. Rodríguez, by grant AGL2013-49164 of the Spanish Ministry for Science and Innovation, to J. Avilla and D. Bosch, and by the CERCA Programme/Generalitat de Catalunya. |
