Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2018, the average hatching date will be ahead of the average, despite having cool April temperatures. 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). Most areas in Iowa have reached peak corn rootworm egg hatch (Fig. 1). Larvae will start feeding on corn roots if available.