Insect Cold-hardiness and Ice Nucleating Active Microorganisms Including Their Potential Use for Biological Control

Since most insects are unable to survive internal ice formation a key factor in their overwintering survival is the regulation of the temperature at which they spontaneously freeze. To enhance their supercooling capacity overwintering insects eliminate endogenous ice nucleators, accumulate low-molecular-weight polyols and sugars, and synthesize hemolymph antifreeze proteins. A number of freeze-tolerant species contain proteins/lipoproteins or insoluble crystals that are ice nucleating active at relatively high subzero temperatures. Only recently have ice nucleating active bacteria and fungi been identified as normal flora in the gut of insects. These microorganisms are the most efficient class of heterogeneous ice nucleators that have been found in insects. Ice nucleating active microorganisms can regulate the supercooling capacity of insects when ingested or applied topically. These unique microorganisms may offer a novel means for the biological control of insect pests during the winter.