Ferrie: Rootworm Featuring Extended Diapause Moves into Illinois

Sticky traps in northwest Illinois are showing Ken Ferrie a picture he had hoped he wouldn’t have to see: populations of northern corn rootworm moving into the state. 

“We saw some of the northern rootworm in fields north of Bloomington this past year, where we usually only see the western specie,” he says. “And in some fields, the northern was the dominant one we saw.”

What makes the northern rootworm so concerning is it can employ an extended diapause.

That simply means it can lay eggs in corn or soybeans one year and they won’t hatch the following year. The eggs will just lay dormant in the soil, and that can complicate control measures.

“Crop rotation is of little help, when eggs don’t hatch,” says Ferrie. He adds that northern corn rootworm eggs can delay hatching for up to five years.

Mother Nature Was No Help
The 2020 derecho may have blown some northern beetles into Illinois from Iowa, though Ferrie says he can’t prove that. One thing is for certain, harvest challenges from down corn last fall added to the rootworm problem. 

“When a 250-bushel corn crop goes down, you’re going to have volunteer corn. Some growers had to spray their volunteer corn as much as three times last year and still didn’t get it all, and that left beetles in the field to lay eggs,” Ferrie says.

He encourages farmers to set out sticky traps this spring to track corn rootworm populations in their fields. “Start taking pictures of what you find, so you can compare them year to year to determine whether the problem’s getting worse,” he says.

If you do have a rootworm issue, talk with your retailer and seedsman about using different traits in 2023 to get a handle on the pest.

If your neighbor has a corn rootworm problem in his fields, find out what control measures he’s using, Ferrie adds. 

“The reason is when the rootworm moves from his field into yours, they will carry any existing resistance to traits with them, so you’ll want to use something different. You’ll have to mix it up,” Ferrie says.

You can hear Ferrie’s complete recommendations on dealing with corn rootworm in this week’s Boots in the Field podcast below: 

New RNAi Technology Takes the Bite out of Corn Rootworm

Unspoken Truths About Pests: Corn Rootworm

Make Pest Scouting a Priority in 2022