Resistance of five field populations of Mythimna separata (Walker) collected from Shaanxi and Shanxi provinces of China to six different insecticides was evaluated by leaf dip method in the laboratory.  The results showed that all populations were relatively sensitive to emamectin benzoate with a resistance ratio (RR) of 0.583–1.583 folds.  All populations showed susceptible or low level resistance to chlorantraniliprole and beta-cypermethrin.  Compared with a relatively susceptible strain of M. separata, the resistance level of the whole populations ranged from susceptible to moderate to chlorpyrifos and lambda-cyhalothrin, moderate to high to phoxim (RR=19.367–70.100) except for population from Sanyuan County (RR=2.567).  Pair-wise correlation analysis among different insecticides indicated that chlorpyrifos has a significantly positive and significant correlation with emamectin benzoate.  Chlorantraniliprole didn’t have significant correlation with emamectin benzoate, chlorpyrifos and phoxim.  Therefore, emamectin benzoate, chlorantraniliprole and beta-cypermethrin are recommended to control oriental armyworm.  Meanwhile, to postpone the occurrence and development of insecticide resistance in Shaanxi and Shanxi provinces, alternative and rotational application of insecticides between chlorantraniliprole and emamectin benzoate or chlorpyrifos is necessary.

 

Plutella xylostella (L.) (Plutellidae) is an important agricultural pest throughout the world.  In this study, the morphology of antennal and mouthpart sensilla in the larvae and adults of P. xylostella (L.) was observed by using a scanning electron microscope.  The larval antennae possess six sensilla basiconica, two sensilla chaetica and one sensillum styloconicum.  Larval mouthparts possess six types of sensilla: sensilla chaetica, sensilla digitiformia, sensilla epipharyngeal, sensilla basiconica, sensilla styloconica and sensilla placodea.  In the adult, seven types of sensilla are found on the antennae in males and six types of sensilla (sensilla basiconica absent) occur in females.  Sexual dimorphism is also found in the number and size of these sensilla on the antennae of adults.  We describe for the first time the five types of sensilla on the mouthparts of the adult of P. xylostella.  This study provides useful information for further research into the function of these sensilla, and better understanding the behavioral mechanisms involved in pest control.