COLD HARDINESS OF PHYTOSEIULUS-PERSIMILIS ATHIAS-HENRIOT AND AMBLYSEIUS-CUCUMERIS (OUDEMANS) (ACARINA, PHYTOSEIIDAE)

Aspects of cold hardiness of Phytoseiulus persimilis Athias-Henriot and Amblyseius cucumeris (Oudemans) were compared. Mean supercooling points (SCPs) ranged from - 19.4 to - 27.1-degrees-C and increased during development from egg to adult. Feeding status, diapause, and low temperature acclimation had little or no effect on supercooling capacity. Temperature/mortality curves confirmed that both species, including A. cucumeris in diapause, are freezing intolerant in the sense that the SCP represents the absolute limit to low temperature survival. However, the mites survived exposure to - 12.5-degrees-C for less than 90 min. The results suggest that the SCP is directly related to body mass in these mites and that their ability to supercool is primarily a physical characteristic rather than an adaptation for survival of exposure to subzero temperatures.