Early Reports Indicate Adult Corn Rootworm Emergence Is Delayed

Mike Gray notes the drought and heavy spring rains are likely key factors in the delayed hatch.

Published on: Jul 15, 2013

By Mike Gray

Although western corn rootworm adult emergence is underway across many central Illinois counties, a quick poll of participants at the DeKalb Research and Education Center field day near Shabbona on July 10 revealed that participants have not observed any beetles moving about their cornfields.

Joe Spencer, an entomologist with the Illinois Natural History Survey, observed larvae continuing their root feeding activity in his research plots north of Urbana on July 9. Based upon these observations, the beginning of our annual root injury evaluations led by Ron Estes, Principal Research Specialist, Department of Crop Sciences, will be delayed about 1 week from our typical mid-July time frame.

Early Reports Indicate Adult Corn Rootworm Emergence Is Delayed
Early Reports Indicate Adult Corn Rootworm Emergence Is Delayed

Reasons for the delayed feeding and emergence this season likely relate to the deeper egg laying during last year's drought and the heavy precipitation this spring and early summer across much of Illinois. Saturated soils do not warm up as rapidly as dry soils and heat unit accumulations, key to the timing of corn rootworm development, have not accrued as fast this growing season.

Joe Spencer also noted lodging in his research plots following some heavy rains and wind that moved through portions of east central Illinois on July 10. On July 17, a field day is scheduled for the Northwestern Research and Education Center near Monmouth.

Producers are encouraged to bring 10 roots from their fields for root injury evaluations. I will have a crew on site to assist with the evaluations and answer any questions.

Mike Gray is an entomologist with the University of Illinois. This article was published in The Bulletin. For the original, click here.