Red crown rot an emerging issue in Illinois

Farmers have reported cases of yellowing soybeans in patches of fields in recent weeks.

And, while much of it could be tied to outbreaks of root rot, phytophthora, soybean cyst nematodes or recent findings of Septoria brown spot on lower leaves, a new issue has emerged that can also result in leaf discoloration.

Carl Bradley, University of Kentucky plant pathologist, said isolated cases of red crown rot continue to move from the Southern U.S. into parts of Illinois, southern Indiana and Missouri.

“This is not a new disease to soybeans, it’s just new to this area,” Bradley said at a University of Illinois agronomy field day at the Orr Agricultural Center near Baylis. “It was reported in Pike County for the first time [of anywhere in the state] in 2018. It has continued to spread.”

Red crown rot, which is caused by a soil-borne fungus, spread to an estimated 22 counties in Illinois last year, mostly in western and southwest Illinois. It causes chlorosis and necrosis of the leaves and a reddish coloration of the lower stem, often resembling sudden death syndrome or brown stem rot.

But the tell-tale sign of red crown rot is the appearance of little, spherical features on the soy plants.

“If you think you have this for the first time, it’s important to send plant samples to the University of Illinois lab,” Bradley told Illinois farmers at the field day. “It’s very important you know what you have in your field.”

Red crown rot can take down soybean plants and cause yield loss. But findings of the disease so far are generally limited to small portions of fields.

“We’ve got hot spots in fields,” Bradley said. “The good news is the fields affected are still yielding OK. The majority of fields are not affected. It’s a very patchy disease based on our observations in Kentucky.”

Seed treatments do provide some protection against red crown rot with at least one fungicide, Saltro, labeled for red crown rot in Illinois and surrounding states. So far, it appears the greatest risk for red crown rot is in later-planted and double-crop soybean fields, Bradley said.

“This is not a new disease to soybeans, it’s just new to this area.”

—  Carl Bradley, University of Kentucky plant pathologist

Corn rootworms popping up

Farmers should also keep an eye out for corn rootworms as adults of that pest are emerging around the state, said Nick Seiter, U of I Extension field crop entomologist.

“This is a good time to inspect fields to get a feel for the extent of your rootworm problem and how your traits/insecticides are performing,” he wrote in an Illinois Soybean Association crop report.

In general, rootworms aren’t a major problem in areas with widespread crop rotations. Seiter noted he could hardly trap any rootworms in the Orr Ag Center research fields.

However, there are areas with continuous corn, particularly in northern Illinois, experiencing significant rootworm outbreaks.

“There’s a very high chance if you’re in a [crop] rotation, you won’t have a major rootworm issue the next few years,” Seiter told farmers at the field day. “What’s concerning is when we find it and screen the insects, we find more with resistance to below-ground traits. So, if you have corn on corn, you’ll need an insecticide.”

This story was distributed through a cooperative project between Illinois Farm Bureau and the Illinois Press Association. For more food and farming news, visit FarmWeekNow.com.