Cold adaptation strategies in lab-reared European grapevine moth Lobesia botrana: Exploring diapause induction, supercooling point, and cold hardiness

The European grapevine moth, Lobesia botrana (Denis and Schiffermueller) (Lepidoptera: Tortricidae), is a significant pest causing economic damage to vineyards worldwide. In this research, the cold tolerance of the pupae and its relationship with diapause was investigated at 23 ± 0.5 °C, 70 ± 5% RH, and LD 12:12 h. One-day-old eggs were transferred to LD 12:12 h to induce diapause at the pupal stage. Diapausing pupae exhibited a mean supercooling point (SCP) of -24.35 °C, whereas in the non-diapausing pupae (23 ± 0.5 °C, 70 ± 5% RH, LD 16:8 h), it was -23.06 °C, with no significant difference between the two groups. Furthermore, diapausing pupae demonstrated significantly higher cold tolerance (LT50 of -14.43 °C) than non-diapausing pupae (LT50 of -3.33 °C). Diapausing pupae tolerated subzero temperatures without significant changes in the SCP, tolerating 11 °C lower than control pupae due to the short daylength alone. Our results suggest that the diapause state and cold hardiness of L. botrana are independent of changes after SCP, and the insect employs a freeze-intolerant strategy to overcome subzero temperatures. Cold acclimation at -5 and -10 °C for 72 h induced a significant decrease in the SCP of diapausing pupae, while a 72-h cold acclimation had no notable impact on the SCP of non-diapausing pupae. These findings provide valuable insights into the survival mechanisms of the European grapevine moth under cold conditions and diapause-related adaptations.