Cold tolerance of biological control agents Amblydromalus limonicus and Amblyseius degenerans

Knowledge about cold tolerance of non-native biological control agents is critical to avoid permanently establishing them in new temperate areas. The cold tolerance of the predatory mites, A. limonicus and A. degenerans, was investigated in the laboratory to assess their establishment potential in northern Europe, particularly Sweden. The lethal time of A. degenerans declined steeply from 5°C to 0°C and was almost zero at -5°C. The lethal time of A. limonicus did not differ between 5°C and 0°C but was reduced at -5°C. For both species, LTime50 was longer for fed than for unfed mites. In the lethal temperature experiments, a temperature as low as -17.75°C was required to achieve a 100% mortality rate for A. limonicus, whereas most A. degenerans died at -8.5°C. LTemp50 was lower for A. limonicus (-9.8°C) than for A. degenerans (-0.1°C). Collectively, these findings suggest that A. degenerans is unlikely to be established in Sweden but that A. limonicus is more cold-tolerant. This highlights the risk associated with releasing A. limonicus in Sweden, due to concerns about potential establishment.

Methods
The dataset was collected during laboratory experiments conducted at the Swedish University of Agricultural Sciences in Uppsala and has been processed by a series of generalized linear models using package stats in R version 4.2.1.