Corn rootworm egg hatch in Iowa can occur from late May to the middle of June, depending on accumulating soil degree days, but the average hatching date is around June 6th. Research suggests about 50 percent of egg hatch occurs between 684-767 degree days (base 52°F, soil). Although Iowa had a warmer than normal March, soil temperatures have been closer to normal in April and May. So the 2012 predicted corn rootworm egg hatch is only slightly ahead of normal (Photo 1), but about two weeks ahead of the 2011 growing season. The southwest region in Iowa is experiencing 50 percent egg hatch now and other parts of the state will approach it within 7-14 days depending on the temperature. Other states have also reported that corn rootworm egg hatch is underway. Illinois is reporting the earliest initial egg hatch in 35 years.
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