Laboratory and Field Investigations on the Ability of Eggs of the European Pine Sawfly, Neodiprion sertifer (Geoffroy) to Withstand Low Winter Temperatures

Publisher Website
Google Scholar
Abstract
Measurements of the supercooling points of eggs from different latitudes suggest that the cold-hardiness of N. sertifer is increased by the selective pressure of low winter temperatures. In Ontario, the insect is only beginning to experience temperatures capable of influencing population trends, but the selection of a more cold-hardy population may be in progress. It is predicted that this insect will eventually be capable of extendng its range into natural stands of jack pine in the northwestern portion of the province.Overwintering eggs are inherently able to supercool to about −26 °C., but exposure to certain non-lethal conditioning temperatures increases their cold-hardiness. Increased cold-hardiness apparently is associated with the appearance of glycerol in the eggs. Mortality curves based on supercooling points of eggs exposed to optimal conditioning temperatures are useful in predicting overwintering mortality of eggs that are not protected by snow cover.