Decreased capture of natural enemies of pests in light traps with light-emitting diode technology

Light traps, containing a fluorescent lamp, are commonly used to control pests in Chinese tea gardens. However, owing to them emitting light with a wide wavelength range, they can also attract and kill numerous natural enemies of such pests, which can potentially threaten the ecological balance of tea gardens. The light source in traps is a key factor determining the species of trapped insects. Based on interspecific differences in the phototactic response to diverse light of narrow wavelength among insects, a light source friendly to natural enemies of pests was designed in this study using light-emitting diode chips. First, the wavelengths corresponding to the peaks of phototactic responses of two major tea pests, Ectropis obliqua (Lepidoptera: Geometridae) (385 nm) and Empoasca onukii (Hemiptera: Cicadellidae) (420 nm), and of 10 dominant natural enemies (380 nm) in tea gardens, were confirmed by indoor bioassays, and then 385-nm and 420-nm light-emitting diode chips were selected to construct the light source for traps. Furthermore, a light trap combining a conical light source with suction fan equipment was designed to increase the quantity and lethality of catches. Finally, evaluation of the performance of the designed light trap was conducted in the field, revealing that it had the desired effect, namely, trapping more tea pests as well as fewer natural enemies compared with light traps with a fluorescent lamp.