Menu

Suspect Corn Rootworm in Continuous Corn? Rotate!

Resistance isn’t just a problem in the western Corn Belt; it’s also a problem in Michigan. The first field with unexpected corn rootworm damage in corn expressing the Bt trait for corn rootworm control was found in 2012 in Michigan. In 2013, more fields were identified. Lodged corn, high populations of corn rootworm beetles, signs of leaf feeding and silk clipping were present in suspect fields. When field histories were examined, a common theme emerged: continuous corn fields that had been planted to either Cry3Bb1 or mCry3A hybrids for multiple seasons.

To preserve the effectiveness of the Bt traits in controlling corn rootworm, we must take action. Before going to the fields this spring, Michigan State University Extension encourages farmers to double-check their cropping plan. Fields where there is suspected corn rootworm damage should be rotated to something other than corn and all volunteer corn should be controlled. Just one year in a non-host crop such as soybeans will wipe out the population. Adjacent fields should also be rotated if possible. If not, monitor for corn rootworm.

In the event the field cannot be rotated out of corn, use a hybrid that either has a totally different Bt trait or use a conventional hybrid with an insecticide to control corn rootworm. MSU field crop entomologist Christina DiFonzo published the Handy Bt Trait Table that helps sort out the different traits available. This and other information on corn rootworm can be found at the MSU Field Crops Entomology website.

Producers of continuous corn are asked to monitor their fields in July for the presence of corn rootworm. Signs include root feeding, corn rootworm beetles, silk clipping, possible leaf feeding, and lodged corn. Report suspected corn rootworm fields to your seed dealer, Christina Difonzo or me, Marilyn Thelen.

To learn more about corn rootworm in the eastern Corn Belt, see “Consensus recommendation: Managing Western Corn Rootworm Resistance to Bt on the Fringe,” a white paper by university field crop entomologists from Michigan, Ontario, Ohio, Indiana, New York and Pennsylvania.

Source: Michigan State University Extension 

Recent News

If you Have Not Been Scouting Corn, Now Is the Time to Start
7/14/2020

Most of Illinois this season has been hot and dry, especially through central and northern portions of the state .  This has been good as far as limiting foliar diseases in our corn crop.  Fungi require some level of moisture for spores to germinate, and the fungus to grow and infect foliage.  This is a major reason […]

Soybean Demand Linked to Economic Recovery
7/14/2020

Wet and warm conditions over some key soybean growing regions pressured soybean prices recently.  The prospect of a good soybean crop places added emphasis on demand over the next year.  Soybean consumption in 2020-21 shows a substantial increase driven mostly by expanded exports in the recent WASDE report.  A robust recovery in domestic and world […]

Western Corn Rootworm Beetles Emerging, Time to Scout
7/13/2020

Western corn rootworm beetles began emerging in southeast and south central Nebraska at the end of June. Beetles typically emerge somewhat later in northeastern and western Nebraska. Beetles emerging before silk emergence may feed on corn leaves. They feed by scraping the surface tissue, leaving a white parchment-like appearance. Once silks emerge, they become the […]

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now