Monitoring field populations of Plutella xylostella (Lepidoptera: Plutellidae) for resistance to eight insecticides in China
Keywords:
resistance, abamectin, Bacillus thuringiensis, beta-cypermethrin, chlorantraniliprole, spinosad, integrated pest managementAbstract
The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is the main destructive insect pest of brassicaceous vegetables around the world. It has developed resistance to various classes of insecticides. However, the current status of insecticide resistance in P. xylostella has not been examined in China. In this study, concentration-mortality responses of P. xylostella to 8 insecticides, including abamectin, chlorantraniliprole, spinosad, beta-cypermethrin, chlorfenapyr, diafenthiuron, chlorfluazuron and the bio-pesticide Bacillus thuringiensis kurstaki (Btk) were evaluated. The results showed that almost all of the tested populations had developed high to very high resistance to abamectin and beta-cypermethrin, with resistance ratios ranging from 62.9 to 1494.7-fold. Chlorantraniliprole was very effective against P. xylostella in most tested populations except those from Taihe and Wuxi. Approximately 61% of tested populations displayed moderate resistance to spinosad, while other field populations showed minor changes (3-fold) in their susceptibility to this insecticide. Obvious variation (93-fold) of susceptibility to chlorfenapyr existed in field populations of which 32% displayed low level resistance, and 36% exhibited moderate resistance. Only one field population (Wuxi) showed very high resistance to chlorfenapyr (RR = 260.1). Diafenthiuron and chlorfluazuron were highly effective against all of the tested populations with resistance ratios (RR) ranging from 0.4 to 8.7 – fold. Decreased susceptibility ranging to moderate resistance to Btk was observed (RR = 3.8 – 35.3). Significant correlations were detected between the values of logLC50 of chlorantraniliprole and 4 insecticides (abamectin, spinosad, beta-cypermethrin and chlorfenapyr). The results of this study provided valuable information for choosing alternative insecticides and for integrated resistance management of P. xylostella.
Resumen
La polilla de la col, Plutella xylostella (L.) (Lepidoptera: Plutellidae), es la plaga principal de insectos destructivos de hortalizas brassicaceous por todo el mundo. Esta ha desarrollado resistencia a diversas clases de insecticidas. Sin embargo, no se ha examinado el estado actual de resistencia a los insecticidas en P. xylostella en China. En este estudio, se evaluó la dosis-respuesta de P. xylostella a 8 insecticidas, incluyendo abamectina, clorantraniliprol, espinosad, beta-cipermetrina, clorfenapir, diafentiuron, clorfluazuron y Btk. Los resultados mostraron que casi todas las poblaciones analizadas habían desarrollado entre alta y muy alta resistencia a la abamectina y beta-cipermetrina, con relaciones de resistencia (RR) de 62.9-1,494.7 veces. Clorantraniliprol fue muy eficaz contra P. xylostella en la mayoria de las poblaciones probadas, excepto los de Taihe y Wuxi. Aproximadamente el 61% de las poblaciones analizadas mostraron resistencia moderada a spinosad, mientras que otras poblaciones de campo mostraron cambios menores (3 veces) en su susceptibilidad a este insecticida. Variación obvia (93 veces) en la susceptibilidad a chlorfenapyr existía en poblaciones de campo de las cuales el 32% está representada bajo nivel de resistencia, y el 36% exhibió una resistencia moderada. Sólo una población de campo (Wuxi) mostró resistencia mas alta a chlorfenapyr (RR = 260.1). Diafentiurón y chlorfluazuron fueron mas eficaces contra todas las poblaciones analizadas, con una tasa de resistencia (TR) de 0.4 hasta 8.7 veces. Se observó una disminución en la sensibilidad de resistencia moderada al biopesticida, Bacillus thuringiensis kurstaki (Bt), (RR = 3.8-35.3). Los resultados de este estudio provee información valiosa para la elección de los plaguicidas alternativos y para el manejo integrado de la resistencia de P. xylostella.
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