The Western Corn Rootworm and Northern Corn Rootworm can attack corn in Colorado. Although both species can be found in corn growing areas across the state, only Western Corn Rootworm is considered an economic problem. The western corn rootworm overwinters in egg stage.
Eggs start to hatch in late spring.
The date depends on soil temperature. Hatch in southern Colorado usually starts in mid May, while eggs in cooler areas do not hatch until early June. After hatching, the small rootworm larvae move to nearby corn roots and begin feeding on root hairs and small roots. Larger rootworms feed on and tunnel in primary roots. Under heavy pressure, root systems can be completely destroyed.