Resistencia a nuevos insecticidas en moscas blancas de cultivos hortícolas
[SPA] La ‘mosca blanca del tabaco’ Bemisia tabaci (Gennadius) y la ‘mosca blanca de los invernaderos’ Trialeurodes vaporariorum (Westwood), son las dos especies de mosca blanca de mayor importancia económica, debido a los graves daños que ocasionan tanto en cultivos hortícolas como ornamentales a nivel mundial. Debido a un uso excesivo de los insecticidas, ambas especies de mosca blanca presentan una enorme facilidad para desarrollar resistencia a numerosos productos, incluso materias activas novedosas han llegado a causar fallos de control por problemas de resistencia. Teniendo en cuenta que cada vez hay menos agentes de control químico eficaces para el control de mosca blanca, es de vital importancia el uso adecuado de los insecticidas disponibles en el mercado, así como la incorporación de diferentes materias activas con nuevos modos de acción. En este trabajo se han determinado los niveles de resistencia a spiromesifén y spirotetramat en diferentes poblaciones de B. tabaci. Cabe señalar, que estas poblaciones fueron recolectadas en invernaderos del sureste español (Murcia y Almería) y que mostraban posibles fallos de control a ambos ketoenoles. En general, la toxicidad a ambos insecticidas varía significativamente entre las poblaciones bioensayadas, mostrando valores de CL50 muy altos en la mayoría de los casos. También se continuó estudiando las posibles resistencias cruzadas entre spiromesifén y los insecticidas de uso común para el control de mosca blanca, a partir de una población seleccionada en laboratorio para la resistencia a spiromesifén (R-SPI). Según los datos obtenidos podemos decir que spiromesifén no presenta resistencia cruzada con ninguno de los insecticidas ensayados. Sólo en el caso de pimetrocina cabe la posibilidad de una resistencia cruzada positiva, aunque parece más probable que la esta resistencia estuviera ya presente en las poblaciones originales de campo. Finalmente, para saber si la resistencia a ambos ketoenoles se trataba de una resistencia metabólica, se llevaron a cabo bioensayos con sinergistas. Nuestros resultados descartaron que las P-450 monooxigenasas, las glutatión S-transferasas y las esterasas estuviesen implicadas en la resistencia a spiromesifén y spirotetramat. De forma general, teniendo en cuenta la ausencia de resistencia metabólica y resistencia cruzada con otros insecticidas con diferentes modos acción, y la existencia de resistencia cruzada entre ambos ketoenoles, todo apunta a que la resistencia a ambos insecticidas sea debida a una mutación en el punto de acción. [ENG] The tobacco whitefly Bemisia tabaci (Gennadius) and the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are whitefly species with a great economic importance because of the serious damage they cause in horticultural and ornamental crops worldwide. In many agricultural systems, the extensive use of insecticides against whitefly pests has resulted in high resistance levels to conventional and novel chemical control agents, causing control failure by resistance development. The ease with which these pest insects develop resistance makes it crucial to implement insecticide resistance management (IRM) strategies. Therefore, new insecticides with different modes of action and no crossresistance with those commonly used must be incorporated into IRM strategies. Firstly, the level of resistance to spiromesifen and spirotetramat in Spanish populations of B. tabaci was determined in this work. The field strains were collected in greenhouses from southeastern Spain (Murcia and Almería) after several years of intensive use of these compounds. In general, toxicity to both insecticides varied significantly between all populations, showing very high LC50 values in most cases. The cross-resistance between spiromesifen and the commonly used insecticides in whitefly control was also studied in a strain further selected from spiromesifen-resistant field populations (R-SPI). According to the results, spiromesifen did not show crossresistance to any of the other insecticides tested. The only exception was pymetrozine, although it is likely that the resistance to pymetrozine was already present in the original field populations. In addition, to determine if whitefly resistance to both ketoenols was metabolic, synergist bioassays were conducted. Our results indicated that cytochrome P-450, glutathione Stransferases and esterases were not involved in spiromesifen and spirotetramat resistance. The lack of a metabolic mechanism and cross-resistance with other modes of action, together with the cross-resistance between both insecticides, suggest a target-site resistance mechanism.[ENG] The tobacco whitefly Bemisia tabaci (Gennadius) and the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are whitefly species with a great economic importance because of the serious damage they cause in horticultural and ornamental crops worldwide. In many agricultural systems, the extensive use of insecticides against whitefly pests has resulted in high resistance levels to conventional and novel chemical control agents, causing control failure by resistance development. The ease with which these pest insects develop resistance makes it crucial to implement insecticide resistance management (IRM) strategies. Therefore, new insecticides with different modes of action and no crossresistance with those commonly used must be incorporated into IRM strategies. Firstly, the level of resistance to spiromesifen and spirotetramat in Spanish populations of B. tabaci was determined in this work. The field strains were collected in greenhouses from southeastern Spain (Murcia and Almería) after several years of intensive use of these compounds. In general, toxicity to both insecticides varied significantly between all populations, showing very high LC50 values in most cases. The cross-resistance between spiromesifen and the commonly used insecticides in whitefly control was also studied in a strain further selected from spiromesifen-resistant field populations (R-SPI). According to the results, spiromesifen did not show crossresistance to any of the other insecticides tested. The only exception was pymetrozine, although it is likely that the resistance to pymetrozine was already present in the original field populations. In addition, to determine if whitefly resistance to both ketoenols was metabolic, synergist bioassays were conducted. Our results indicated that cytochrome P-450, glutathione Stransferases and esterases were not involved in spiromesifen and spirotetramat resistance. The lack of a metabolic mechanism and cross-resistance with other modes of action, together with the cross-resistance between both insecticides, suggest a target-site resistance mechanism.
Insecticidas, Protección de cultivos, Gestión de la producción vegetal, Hortalizas, Insecticides, The tobacco whitefly, Bemisia tabaci (Gennadius), Agricultural systems
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