Thermotolerance in a spider mite: implications in disinfestation treatment

Tetranychus ludeni Zacher is a European spider mite species and an important invasive pest in horticulture. We investigated the effects of hot air on its survival and reproduction, providing knowledge for development of disinfestation programs using heat. We tested how each life stage responded to heat treatments of five air temperatures (45 to 57°C) and five exposure durations (three to 15 hours). We showed that no eggs hatched after exposed to 45°C for ≥ 15 hours, 48°C for ≥ 12 hours, or 51°C for three hours; no adults survived 51°C or 54°C for ≥12 hours or 57°C for ≥ six hours, and heat tolerance of other life stages fell in between. Higher temperature and longer exposure time also reduced developmental success and fecundity. These findings suggest that we may be able to eradicate the mites of all stages using one hot air treatment at 57°C for six hours or two treatments at 51°C for three hours at a 10-day interval to kill all eggs in the first treatment and those laid by survived adults in the second. The eradication strategy using hot air of 51–57°C may be more suitable for treating plant residues on exported/imported machinery, farm equipment and containers because it may have negative impact on fresh postharvest products. With the knowledge that exposure to 45°C substantially reduced the mites’ fecundity, particularly when the younger stages were treated, we suggest that heat treatment of fresh postharvest products with 45°C could still greatly reduce the quarantine risk of this pest.