Ohio State University researchers are asking soybean farmers in the state to check their crops for red crown rot.
The issue is caused by a soil-borne fungus that can persist in fields for years. Researchers hope to get early detection and an accurate diagnosis to stop the problem from spreading.
WOSU’s Debbie Holmes spoke with Horacio Lopez-Nicora, an associate professor of soybean pathology and nematology at Ohio State.
Debbie Holmes: How does this fungus get into the soil?
Horacio Lopez-Nicara: It's a soil-borne pathogen. It inhabits the soil. It moves with movement of soil. So, anything we do to move the soil either naturally by wind or water movement or by anthropogenic movement, which means that soil that we humans will move around with machinery, going in a field and taking soils and moving it around, that's how the fungus will move around and infest where it was not present before.
Debbie Holmes: Now is this also part of warm and wet conditions?
Horacio Lopez-Nicara: The fungus is more severe under warmer soil conditions. Soil temperatures that average on 77 degrees Fahrenheit will be optimal for this fungus to cause very damaging and severe effect on soybeans.
Debbie Holmes: Why does it affect soybeans in particular?
Horacio Lopez-Nicara: The fungus actually has a wide host range. It can affect peanuts, for example, in the southern part of the United States. It was a big issue in peanuts. It can affect other legumes. Rotating to grass is a good strategy to lower the population of the fungus. So, it can really go to other hosts as well, specifically legumes. Alfalfa, for example, could be a host for this fungus. Soybean is a very important agronomic crop that we plant in Ohio and is very susceptible, unfortunately.
Debbie Holmes: So where did the name "red crown rot" come from?
Horacio Lopez-Nicara: The symptoms that this fungus causes when it produced that disease, which is called "red crown rot," is a red discoloration on the crown of the plant, on that area that meets the soil line. So, the stem goes all the way down and, in that area, that meets soil, which we call the crown and of the plant, that's where a very red discoloration takes place. In addition to that, the fungus can produce under conducive conditions, sexual fruiting bodies that are called periphecia. These are round, red fruiting bodies, giving that reddish coloration of the stem of the plant and even more red symptoms.
Debbie Holmes: What do you want farmers to do to help alleviate the problem?
Horacio Lopez-Nicara: We want farmers to walk their fields. We want farmers to scout their fields, specifically, when they see plants that are showing abnormal growth, or where they see plants that are sick and dying, examine that crown area of the plant. Now, this disease unfortunately causes symptoms that resemble other diseases that we're very used to managing in Ohio. The fact that this is an emerging disease that is new in Ohio and in the north central region, and it's causing the same symptoms of other diseases that we know how to manage. It's very dangerous because the management for this disease is very different than the other ones. For us, thinking that we have a disease that we're used to managing and not going and examining the plant and actually diagnosing that it is red crown rot, it can just allow these fungus and disease to continue growing and being more severe in that field and causing more yield reduction. So, accurate diagnosis is what we're asking for. Send a sample to Ohio State Diagnostic Labs and we'll help with diagnostics.
Debbie Holmes: Any idea how widespread this problem is in Ohio?
Horacio Lopez-Nicara: We don't know. We have fields that we have confirmed the presence and damage of this disease. However, we don't know how (wide) spread it is in Ohio.
Debbie Holmes: What does this problem mean for farmers then and their soybean profits as well as the prices of soybean products at the grocery store?
Horacio Lopez-Nicara: So, the fungus is an extremely successful root rotter. It completely eats and chews and destroys the root system of the plant and therefore reduces yield significantly. In the field that we have reported this in Ohio, on average, we were quantifying a 35% yield reduction. That's huge. And other places where significant development of this disease happened, some of the reports are 70%, even more.
