While there have been no reports in Ohio of resistant rootworms, growers may want to keep a sharp eye out for any significant lodging as it could be a sign that the pests are indeed present, says Andy Michel, an Ohio State University Extension entomologist.
The concern is that the western Corn Belt has been experiencing greater than expected damage on Bt-corn expressing the single trait Cry3Bb1, with most of these observations found in continuous corn, says Michel.
"At this point we haven't found it in Ohio yet, but the problem is spreading and we expect it to be in Ohio at some point," he says. "So we're trying to inform growers that this issue is a growing problem and trying to get the word out so that we can be first responders to any cases that pop up in Ohio.
"So our goal is to try to catch it early to wipe it out before it can continue its spread."
The problem has grown because western corn rootworms have evolved resistance in the Corn Belt and the problem is spreading, particularly in some hotspots that then spread outward.
"The situation throughout the western Corn Belt is serious and the financial implications could be quite significant," he said. "Growers pay a premium for transgenic corn varieties so they expect rootworm control.
"But if they are experiencing Bt-resistant rootworms, they are not only losing money because of the premium, but also on yields. Western corn rootworm in North America is the No. 1 insect problem corn growers are facing."
Corn growers in Ohio can look out for significant lodging during harvest.
"Detecting damage caused by rootworms is often difficult at this late stage of the season," Michel says. "Many factors can cause lodging including wind damage and poor root growth, so a careful examination of the roots is necessary.
"If you see lodged corn, dig up the roots and if it looks like there are short roots or roots that have been chewed on or gnawed on. It could be from rootworms."
Growers who find this or aren't sure if what they are seeing is indicative of western corn rootworm damage, can contact Michel at email@example.com or Ron Hammond, an OSU Extension and OARDC entomologist, at Hammond.firstname.lastname@example.org with questions.