Insecticide Resistance In The Common Cutworm, Spodoptera Litura (Fabricius) And The Possible Mechanisms

The common cutworm, Spodoptera litura (Fab.), is a worldwide pest with an extensive host range and especially infests some important crops including tobacco, cotton, soybean and many vegetables. It formerly broke out only intermittently in China. Since the early 1990s, however, common cutworm has reached large number every year and large amount of insecticide have been used for combating its infestation on crops. As a result, many field populations of this pest have developed multiple resistances, which make more and more frequent control failures in field. However, though some related work has been done, there is still not a suitable method and enough toxicity baseline data for monitoring of the resistance in this pest. Lacking of the knowledge of resistance mechanism is also the barrier for implementation of resistance management and efficient control. In this paper, efforts have been made to develop a suitable resistance monitoring method and declare its resistance mechanism, inheritance model, and fitness costs. The results obtained are summarized as follows:1 Resistance monitoring methods and the corresponding toxicity baseline dataA susceptible strain of S. litura was selected by single egg cluster selection of a laboratory strain. More efficient topical application and leaf dipping methods were developed with 3^rd instar larvae as test animals, and the corresponding toxicity baselines of more than 10 convenient insecticides were also established with this susceptible strain as standard. Further resistance monitoring practice with field populations showed that topical application method was much sensitive for monitoring the resistance to contact insecticides, and leaf dipping method for that to the insecticides with stronger stomach action. But both worked well in monitoring resistance. As compared with those methods used previously, the newly developed methods were not only accurate, but also efficient and with less labor and time consume. Moreover, a lot of corresponding toxicity baseline data was provided. So, it was confident to recommend these methods for application in the further work.2 Resistance of field populations to common insecticidesThe insecticide resistance was monitored with the insects collected from Nanjing...