Dolors Bosch1, Marcela A Rodríguez2, Jesús Avilla3. 1. Departament de Protecció Vegetal Sostenible, Institut Recerca i Tecnologia Agroalimentària (IRTA), Lleida, Spain. 2. Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile. 3. Department of Crop and Forest Sciences, Agrotecnio, Universitat de Lleida, Lleida, Spain.
Abstract
BACKGROUND: Widespread resistance of Cydia pomonella to organophosphates was demonstrated in populations from the Spanish Ebro Valley area which showed high levels of enzymatic detoxification. To determine the efficacy of new insecticides, neonate larval bioassays were carried out on 20 field codling moth populations collected from three different Spanish apple production areas. Synergist bioassays were performed to determine the enzymatic mechanisms involved. RESULTS: The least active ingredients were methoxyfenozide, with 100% of the populations showing significantly lower mortality than the susceptible strain, and lambda-cyhalothrin, with very high resistance ratios (872.0 for the most resistant field population). Approximately 50% of the populations were resistant or tolerant to thiacloprid. By contrast, tebufenozide was very effective in all the field populations, as was chlorpyrifos-ethyl despite its widespread use during the last few years. Indoxacarb, spinosad and chlorantraniliprole also provided high efficacy, as did emamectin and spinetoram, which are not yet registered in Spain. CONCLUSION: The resistant Spanish codling moth populations can be controlled using new reduced-risk insecticides. The use of synergists showed the importance of the concentration applied and the difficulty of interpreting results in field populations that show multiple resistance to different active ingredients.
BACKGROUND: Widespread resistance of Cydia pomonella to organophosphates was demonstrated in populations from the Spanish Ebro Valley area which showed high levels of enzymatic detoxification. To determine the efficacy of new insecticides, neonate larval bioassays were carried out on 20 field codling moth populations collected from three different Spanish apple production areas. Synergist bioassays were performed to determine the enzymatic mechanisms involved. RESULTS: The least active ingredients were methoxyfenozide, with 100% of the populations showing significantly lower mortality than the susceptible strain, and lambda-cyhalothrin, with very high resistance ratios (872.0 for the most resistant field population). Approximately 50% of the populations were resistant or tolerant to thiacloprid. By contrast, tebufenozide was very effective in all the field populations, as was chlorpyrifos-ethyl despite its widespread use during the last few years. Indoxacarb, spinosad and chlorantraniliprole also provided high efficacy, as did emamectin and spinetoram, which are not yet registered in Spain. CONCLUSION: The resistant Spanish codling moth populations can be controlled using new reduced-risk insecticides. The use of synergists showed the importance of the concentration applied and the difficulty of interpreting results in field populations that show multiple resistance to different active ingredients.