Early stages of red crown rot research

JOHNSTON, Iowa — With the recent emergence of red crown rot on soybeans, management options are limited and no rescue treatments are available to mitigate the plant damage once infection has been detected.

Robert Bellm, retired University of Illinois Extension crops systems educator and agronomist in southern Illinois, noted his experiences with red crown rot during a recent podcast hosted by Pioneer.

Bellm was asked what experiences he has in trying to control red crown rot at this early point in the disease’s arrival.

“I wish I had a good answer to that. It has occurred on our area in fields that have had at least the soybean cyst nematode rate of ILeVO on them. So, whether ILeVO is having any benefit or not, interestingly enough, and I can’t prove it one way or the other,” Bellm said.

“But I think in some cases the fields I have looked at that had ILeVO on it, the red crown rot seems to be more prevalent. So, what I think is happening with ILeVo is it’s suppressing SDS and therefore red crown rot becomes more obvious. Not that it’s helping red crown rot, but just makes it easier to find in those fields. I can’t prove that, but it seems to happen. I’ve found it in fields that had a full rate of ILeVO on it.

“So, I think where some of the research needs to start to focus on is are there any management techniques, at least on the chemical side, that’s going to work.

“University publications always say to select resistant varieties. Well, we don’t know if there are any resistant varieties for red crown rot.

“It’s recommended to rotate out of soybeans to non-host crops. It’s like SDS or any of the other soil-borne organisms. They’re persistent in the soil. I’m not sure that rotation is going to make a whole lot of difference.

“So, until awareness of this disease becomes widespread enough that research is done, we’re kind of struggling on this.

“I think the first task is for growers to identify whether or not they have a problem and then go from there.”

Research

Scott Eversgerd, Pioneer field agronomist in western-southern Illinois, said there hasn’t been a lot of variety screening done “at a level that could be very consistent and give us good data.”

“We’re actually finding that out in the field probably better than research right now, although research is starting to move,” he said.

“At Pioneer now we’ve identified this as a potential major issue and we’re starting to move in a direction to do some pre-commercial screening that should help us.”

Brad Mason, Pioneer field agronomist in western Illinois that includes Pike County, where the fungal disease was initially confirmed in Illinois in 2018, said field trials is currently underway adjacent to where the disease was first found.

“To give you an idea of how anxious those growers were there, they were meant to go to corn this year. They’re going to put half of that field in soybeans because they want to have an (Intensively Managed Product Advancement Characterization and Training) trial there for them to screen,” Mason said.

“They’re worried about deer, so they’ve even going to put up a hot wire to make sure to keep the deer out because they want to start making some advances. They get so worried about this disease.

“It’s hit them hard enough and we have growers over there that aren’t doing soybeans this year because of the hit from this. These guys I’m talking about will actually bleach their planter from field to field. They’re that worried about it.”

Bellm’s advice is as soybeans reach R3 and sudden death syndrome-like symptoms appear, start digging.

“Get out into those areas, get on your hands and knees, pull some plants up and look. If you have any questions, contact either your Pioneer agronomist or at least your dealer and have them contact the agronomist,” Bellm said.

“Get some plants sent to the U of I plant clinic or someone else, get it identified and them we can start to go from there.”

Origin

Bellm noted some literature indicates red stem rot may have arrived in the United States on indigo plants about a century ago. Indigo was grown in the southern United States.

Dye is obtained from processing the legume plant’s leaves.

“When the indigo market disappeared, they started planting peanuts and soybeans. It jumped over to that. So, it probably has a wider host range than we’re aware of,” Bellm noted.

“From what I read, it first showed up in the country probably as a peanut disease in 1968. It was identified under a different name in peanuts, black rot. It was discovered in about 1972 that it would go over into soybeans and was called red crown rot at that point.

“If that was the origin in the south, how it got up into this area, who knows? It has to move on soil, so anything that can move soil can theoretically move the disease.”