Insecticide susceptibility and enzymatic activity of Cydia pomonella L. (Lepidoptera: Tortricidae) from three apple orchards of Maule Region, Chile | Susceptibilidad a insecticidas y actividad enzimática de <em>Cydia pomonella</em> L. (<em>Lepidoptera: Tortricidae</em>) Proveniente de Tres Huertos de la Región del Maule, Chile

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English. <em>Cydia pomonella</em> L., the major pest of pome fruits and walnuts in Chile, has been controlled almost exclusively with applications of organophosphates insecticides. However, during the last few seasons, increasing levels of fruit damage at harvest have been observed. Given that this insect has evolved insecticide resistance in several countries, the susceptibility to diagnostic dosages of azinphos methyl and tebufenozide were evaluated on diapausing larvae in populations from three apple orchards in Maule Region and one susceptible laboratory strain (S); as well as the activity of detoxifying enzymes on adults emerging from the aforementioned. Both mixed function oxidases (OFM) and glutathione-S-tranferases (GST) activities were evaluated by fluorometry, while esterase activity (EST) was determined by absorption. Larval mortality for azinphosmethyl was significantly lower in the populations from Molina and Teno (30 and 85.4%, respectively) than in the susceptible laboratory strain (95.3%). For tebufenozide larval mortality was significantly lower in the Molina strain (35.1%) than the S strain (88.6%). GST activity was statistically higher in two of the three analyzed orchards (13,679 fluorescence insect-1 units in Teno, and 13,096 fluorescence insect-1 units in Molina). Similarly, OFM activity was significantly higher in the same orchards, with values of 25.08 and 17.95 picograms (pg) of 7OH insect-1 min1 in Molina and Teno, respectively. The S strain had significantly higher EST activity in relation to the other populations, which seems to be unrelated with lower susceptibility to the insecticides evaluated