Impact of Ultraviolet-A (UV-A) radiation on antioxidant enzyme activity in <i>Loxostege sticticalis</i> (Lepidoptera: Pyralidae)

The beet webworm, Loxostege sticticalis Linnaeus (Lepidoptera: Pyralidae), is a devastating insect pest of agricultural crops in northern parts of China. Ultraviolet-A (UVA) radiation, which ranges between 315 and 400 nm, has been broadly used as an illuminance source in light traps since it induces oxidative stress in insects by increasing reactive oxygen species production. The current study aimed to investigate the impact of UVA (365 nm) LED light on oxidative stress marker enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione-S-transferase (GST), and glutathione reductase (GR), in male and female adults of L. sticticalis under different exposure times: 0 (control), 15, 30, 60, and 120 min. For both sexes, total antioxidant capacity (T-AOC) was also calculated. We observed that T-AOC and the activities of oxidative enzymes increased steadily from baseline, peaking at 60 min and then returning to baseline at 120 min for both sexes. This indicates that prolonged exposure to UVA LED light can activate detoxifying enzymes which may hinder L. sticticalis' ability to break down pesticides, resulting in increased sensitivity to insecticides. The degree of response to oxidative stress also differed across different exposure times for both sexes. We concluded that extended exposure to UVA LED light can induce oxidative stress, affect protein functionality, and disturb the physiology of L. sticticalis. Our findings may help establish the theoretical and scientific basis for understanding the mechanism that drives phototaxis in nocturnal moths like L. sticticalis and contribute to the development of novel, sub-lethal, and eco-friendly pesticides.