ENHANCING OVERWINTERING MORTALITY OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) BY MANIPULATING THE TEMPERATURE OF ITS DIAPAUSE HABITAT

Experiments were conducted to evaluate the potential of using an artificially mulched trap crop to arrest adult dispersal of Colorado potato beetle, Leptinotarsa decemlineata Say, in the fall in a location that could be disturbed easily to expose adults to thermal shock and increased overwintering mortality. Four overwintering treatments were established in a trap crop of late-planted potatoes: mulched with wheat straw and not disturbed until spring, mulched but mulch and snow removed during an intense cold front and mulch either replaced or not after 3 d, and unmulched control. Colorado potato beetles were excavated in the spring and survival was assessed: Eighty percent were recovered in the top 25 cm soil strata. Removal of mulch covers rapidly depressed soil temperatures at all depths. In the 0-15 cm soil strata, where most of the adults overwintered, temperatures dropped from 0 to -11.7-degrees-C, whereas in undisturbed plots, temperature remained close to 0-degrees-C. Adult survival was significantly higher in snow-covered, unmulched controls and mulched habitats (almost-equal-to 26%) than in disturbed habitats (almost-equal-to 7%).