In 2011, corn rootworm egg hatch was delayed because of cool soil temperatures. But there have been reports of significant root pruning in some areas of Iowa. In addition, Mike Gray from the University of Illinois has also reported higher root damage in his research plots than in recent years.
I highly recommend digging roots and assessing any corn rootworm injury. You should be able to assess rootworm activity in fields now. Non-Bt fields are most susceptible to larval damage and should be considered a priority. Continuous Bt corn fields with previous damage should also be scouted. Sample corn plants in different areas of the field to estimate infestation levels.
Use this interactive website to learn how to rate corn rootworm injury.
Severe root pruning can interfere with nutrient uptake and make corn unstable.
Photo by Jon Tollefson.