Effect of Photoperiod and Temperature on the Induction and Termination of Diapause in Lygus pratensis (Hemiptera, Miridae)

Lygus pratensis is an important pest of cotton in the Xinjiang Uyghur Autonomous Region, Chana. Diapause plays a key role in seasonal survival, population dynamics, and spring population establishment of this species; therefore, understanding the environmental cues regulating diapause is essential for improving population prediction and developing more effective control strategies. In this study, we investigated the effects of temperature and photoperiod on diapause induction in L. pratensis and further examined how temperature, photoperiod, and duration of cold exposure influence diapause termination. Female ovarian development and the proportion of females carrying eggs were examined under different combinations of temperature and photoperiod. The results showed that both temperature and photoperiod significantly affected diapause induction. The highest diapause rate, 88.33%, occurred when adults were reared under a short photoperiod of 9 L:15 D at 16 °C. In contrast, only 3.33% of females entered diapause under a long photoperiod of 15 L:9 D at 20 °C. Diapause termination experiments indicated that temperature significantly affected the time required for diapause termination, but not the final termination rate. Photoperiod also influenced diapause termination at 24 °C, with termination rates of 44.44% under 8 L:16 D and 100% under 16 L:8 D. However, the duration of exposure to low temperature at 4 °C had no significant effect on diapause termination. These findings demonstrate that temperature and photoperiod are the key environmental factors regulating diapause induction and termination in L. pratensis. Moreover, diapause termination in this species appears to be controlled mainly by environmental cues rather than by a required period of cold exposure. This study provides a biological basis for predicting seasonal population occurrence and optimizing management strategies for L. pratensis in cotton-growing regions of Xinjiang.