Effect of ultraviolet on the environmental adaptability of <i>Megalurothrips usitatus</i> (Thysanoptera: Thripidae)

Megalurothrips usitatus Bagnall, an important pest of bean plants, is primarily managed with synthetic insecticides. M. usitatus has developed considerable resistance to various insecticides in multiple cowpea-growing areas in Hainan Province, China, posing challenges to its control in the field. Light control technology is a potentially effective physical control method for M. usitatus. The vision of thrips is highly sensitive to UV light, whereas other biological characteristics remain unknown. Therefore, this study evaluated the effects of ultraviolet light on the biological characteristics of M. usitatus. Results showed that the egg, larval, and pupal stages of M. usitatus were significantly shortened, and the emergence rate (79.59%) and adult survival rate (77.95%) were reduced under a devoid of UV light environment (UV-), compared with the full-spectrum light (control treatment group, CK) (p < 0.05). However, the single spawning quantity and total amount of spawning were significantly higher, and the sex ratio (57%) was the highest under UV- (p < 0.05). Single UV light (UV+) only affected the pupation rate. Also, the antioxidant enzymes, polyphenol oxidase, superoxide dismutase (SOD), and peroxidase activities were significantly and negatively correlated with the progression of generations under UV-, whereas catalase and SOD activities were significantly and positively correlated with the progression of generations under UV+. The UV- light conditions significantly interfered with the behavior selection of M. usitatus. The results of this study showed that the adaptability of M. usitatus populations would be greatly reduced in the absence of ultraviolet light, providing a theoretical basis for the control of M. usitatus populations.