Survival mechanisms of insects in cold climates are reviewed with particular reference to soil-dwelling insects subjected to freeze-thaw processes. Current knowledge of soil temperature effects on corn rootworm overwinter survival is summarized. Depth of oviposition by corn rootworms varies within the top 30 cm of the soil profile, in response to availability of soil moisture and presence of drought cracks as oviposition sites. Overwinter mortality from the effects of subfreezing soil temperatures also may vary with depth of frost penetration in relation to depth of egg placement. This hypothesis was tested in an experiment in which frost penetration was induced in soil columns containing rootworm eggs at various depths. Mortality of eggs following exposure to frost and subfreezing temperatures was determined. Implications of findings in relation to winter survival, snow cover distribution, and spatial variability of corn rootworm populations in the field are discussed.

M.M. Ellsbury
USDA, ARS
Northern Grain Insects Research Laboratory
R. R. # 3
Brookings, SD 57006 USA
Telephone: 605-693-5212                      
Fax: 605-693-5240
E-mail: mellsbur@ngirl.ars.usda.gov