The Effect of Low Temperatures on some Predacious Phytoseiid Mites, and on the Brown Mite Bryobia arborea M. & A.

Abstract

The mean freezing point of adults of T. pyri was about −20° F., of T. finlandicus −22° F., and of T. rhenanus −24.5° F. The responses of T. fallacis and P. macropilis to low temperatures were about the same as T. pyri. The effect of the duration of exposure on the last three species was to increase the mortality about 12 to 15 per cent for each doubling of the duration of exposure from 0.5 to eight hours at −10° F. or lower. The phytophagous brown mite, B. arborea, had a mean freezing point of −26° F. and the effect of duration of exposure was to increase the mortality eight to ten per cent each time the period of exposure was doubled from 0.25 to 16 hours at −24° F. or lower.