Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average hatching date of June 6. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50 percent of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Cooler spring temperatures mean slower egg maturation in 2014. But a few areas of Iowa are approaching 50 percent corn rootworm egg hatch now (Fig. 1), particularly around Muscatine. Many other regions will be reaching 50 percent egg hatch within two weeks.