Comparison of Phototactic Behavior between Two Migratory Pests, Helicoverpa armigera and Spodoptera frugiperda

SIMPLE SUMMARY: The light trap is a pesticide-free method for pest control. Appropriate wavelength and light intensity are the key factors for trapping specific target pests. However, present light-trapping methods mainly use UV light, which is effective with Helicoverpa armigera and many nocturnal insects and has displayed a low effect on an important migratory pest, the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae). In this study, a series of phototactic behavioral assays were carried out and physical parameters were included to identify the different phototactic behaviors between S. frugiperda and H. armigera. It was found that S. frugiperda had the highest average phototactic rate to blue light than other lights. The phototactic rates of the two moths increased gradually with light intensity and were not obviously influenced by sex. Meanwhile, phototactic rates of S. frugiperda were significantly lower than those of H. armigera at a low light intensity of UV light. Combined with these results and the obtained formula, we summarized a proposal of using blue light for light traps to control S. frugiperda. These results provide an experimental and theoretical basis for improving light-trapping techniques for managing S. frugiperda. ABSTRACT: The fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is an important migratory pest, causing great losses to agricultural production. Light trapping is a pesticide-free method for pest control and is influenced by many factors, especially wavelength and light intensity. In this study, a series of phototactic behavioral assays were carried out and the physical parameters were included to identify phototactic responses of S. frugiperda, with Helicoverpa armigera as control. It was found that S. frugiperda showed the highest average phototactic rate to blue light among five different LED lights. The phototactic rates of the two moths increased gradually with light intensity and were not obviously influenced by sex. In addition, the phototactic rate of S. frugiperda was significantly lower under a low light intensity of UV light than that of H. armigera, further confirmed by the indoor simulation experiment and EC50. According to the obtained parameters, the trapping distance of S. frugiperda to blue light was smaller than that of H. armigera to UV light. Therefore, we summarized a proposal of using blue light for light traps to control S. frugiperda, with a maximum distance of no more than 108 m. These results provide an experimental and theoretical basis for improving light-trapping techniques for managing S. frugiperda.