07/10/25 White Mold Watch: Timing, Treatment & Tactics
You're listening to In The Pod, soybean updates, a weekly trek into the latest soybean information from NDSU Extension. Today, we're talking about a particular fungus that can plague soybeans, white mold. What is it? Where does it come from, and how is it managed? Wade Webster, NDSU Extension plant pathologist, has the facts. Wade, what exactly is white mold?
Wade Webster:Yeah. So white mold is a fungus called Sclerotinia sclerotiorum, and it causes disease on many different crops, mostly the broad leaves. So when we're thinking about production in the state of North Dakota, soybeans definitely come to the top of mind, but we also have sunflowers, canola, dry beans as well. So multiple different crops can be infected by this pathogen leading to the same disease that is white mold.
Bruce Sundeen:How does infection occur?
Wade Webster:Yeah. So this infection is very important to understand the environmental considerations here. This pathogen does require very cool weather conditions, especially at nighttime. So if we're thinking about fifties into the sixties, we need consistent moisture. So not just one heavy rainfall event, but we need moisture to be present on that soil surface for extended period of time. That could be one to two weeks. So if we're getting a couple of different rain showers, then that can lead to increased risk for infection. These sclerotia, what we call the overwintering structures of this pathogen, they will form little cups, what we call apothecia, and those release bursts of spores into that under canopy. And when those spores come in contact with flower tissue, those flowers will become infected and allow for this pathogen to infect into that stem. When that stem then becomes infected, that white mold growth starts to show up about one to two weeks after that initial infection. And so that flowering period is incredibly critical for thinking about managing this particular disease.
Bruce Sundeen:Is a history of infection in a field important?
Wade Webster:White mold is a, what I call, consistently inconsistent, meaning that it is always here in the state, but it's very inconsistent on what areas of the state get impacted by it every year. Just because it is so dependent upon that environmental conditions, the moisture is gonna be playing the biggest factor here. So if we have some spotty showers, especially during that flowering period, those areas are gonna be the most likely to have high levels of white mold develop that year. If we miss rainfall events during that flowering period, then we're not gonna see as much white mold develop. That's why it's pretty inconsistent, but it's consistently across the state every single year.
Bruce Sundeen:Wade, how do you manage white mold?
Wade Webster:Yeah. So management is very important and this is definitely the time to be thinking about that. At this point, fungicides and different pesticide applications will be most critical, again, during that flowering period. If we apply those before flowering, we're gonna miss that window, and if we apply it after that flowering period, we're also gonna miss that window. For white mold management, everything is prevention. We need to make sure that that environment is conducive and those flowers are present, and we also need canopy closure to be present, most cases for white mold management in soybeans. There's multiple different fungicide products out there and available. There are some products with better efficacy with a higher price point, but all of this information is available through NDSU Extension and specifically looking through doctor Michael at NDSU Carrington has a lot of great information on this as well.
Bruce Sundeen:Thanks, Wade. Our guest has been Wade Webster, NDSU Extension plant pathologist. You're listening to In the Pod, Soybean Updates, a weekly trek into the latest soybean information from NDSU Extension supported by the North Dakota Soybean Council.
