VIABILITY AND HATCHING PATTERN OF EGGS OF THE WESTERN CORN ROOTWORM EXPOSED TO CHILL PERIODS OF DIFFERENT DURATIONS

After a chill (5°) period of >16 weeks, the mean post‐chill time to initial hatch of eggs of the western corn rootworm, Diabrotica virgifera, was 19 days; peak hatch occurred a mean of 5 days after the initiation of hatch, and hatch lasted a mean of 5 weeks. The post‐chill time to initial hatch was influenced negatively by chill periods lasting up to ca. 3 weeks; however, chilling for >3 weeks and <60 weeks did not significantly affect the time to initial hatch. The duration of hatch was not significantly altered by chill periods up to 4 weeks, but it was significantly reduced after 8 and 12 weeks of chill. Chilling for 16 or more weeks, however, no longer had an effect. The viability of rootworm eggs was not influenced by chill periods up to 12 weeks, but, as chill periods were extended beyond 16 weeks, the eggs slowly begin to lose viability; over a period of about a year, the viability had been reduced by 80%.