Predicting Spring Hatch of the Alfalfa Weevil1

Abstract

To predict the timing of sprays for control of Hypera postica (Gyllenhal), we initiated a field and laboratory stady using temperature accumulation to determine the time of egg hatch at Dixon Springs and Urbana, Illinois. Because of extended oviposition and the presence of eggs throughout the fall, winter, and spring, the temperature accumulation expressed as degree-days was determined for each stage of development. We found that alfalfa weevil eggs require 313 degree-days to hatch. During the spring of 1969 we were able to predict closely that eggs sampled on January 20, 1969. would hatch on April 3, 1969.