FACTORS INDUCING DIAPAUSE IN HYPHANTRIA CUNEA

Abstract

Diapause induction in Hyphantria cunea is under the joint control of photo-period, temperature, humidity, food quality, and possibly other variables, but insufficient data are available to permit a precise evaluation of their actions and interactions. Short daylength and low temperature induce diapause and the critical thresholds for New Brunswick – Nova Scotia populations are in the vicinity of 14.3 hours and 72°F, respectively. Low humidity increases the incidence of diapause, as does also the change in the nutritional quality of foliage late in the season. Both field data and the extrapolation of laboratory data to field conditions indicate that the occurrence of a partial second generation is unlikely in this area, even in warm seasons.