Winning the War Against White Mold, Part 2 Disease Management

This is a three-part series on Winning the War Against White Mold.
Click here to read Part 1—Disease Development.

By Dusty Sonnenberg, CCA, Field Leader, a project of the Ohio Soybean Council and Soybean Check-off

White mold disease management begins with understanding the conditions that must be met for white mold to infect a susceptible soybean crop. “Once white mold has been identified in a field, or we are concerned about white mold developing, we have quite a few options for management of the disease,” said Dr. Wade Webster, Assistant Professor, Soybean Pathology, North Dakota State University. “The use of chemical applications is primarily where a growers attention will turn. For these applications we have a number of fungicide options and one herbicide option. That herbicide has the active ingredient lactofen. It has been shown to have active control of white mold to certain levels.”

Application timing is important for successful disease control. “Growers will want to make a fungicide application around the R2 growth stage, which full flowering,” said Webster. “If we observe canopy closure in the crop, we may want to make the chemical application earlier than full flowering. Once the application is made, if the environmental conditions persist for prolonged periods of time, growers may want to consider an additional application two weeks later if the field has a history of white mold.”

There are numerous fungicide options available. Universities have conducted fungicide trials and put together a table listing the fungicide products and efficacy details. There is also a smart phone app called Sporecaster that can be used to help make localized decisions for a fungicide application based on the weather conditions. “This app simplifies the decision-making process and is free for growers and has been validated across the entire Midwest and continues to be improved over time,” said Webster.  

Outside of chemical control, there are other disease management strategies. “Crop rotation is an important tool and the first thing we think about in disease management,” said Webster. “There are a lot of important crops and weed species that can serve as a host to white mold. If the field has a history of white mold, growers should avoid other broad leaf or dicot crops. All the small grains and corn are not host crops and make good alternatives in a rotation. Long term rotations are also important as the white mold sclerocia can survive for up to 10 years.”

Another disease management strategy is tillage. “Tillage is an important tool for future white mold disease management if we can get it done early in the fall and incorporate the sclerocia into the soil,” said Webster. “Once the sclerocia are incorporated, they will begin to be eaten by the fungi and bacteria and microbes in that soil. Shallow tillage is best because this is where those microbes live. Deep tillage buries the sclerocia deeper where the bacteria and fungi and microbes do not reside. Given their hard structure the sclerocia can survive and actually be brought back up to infect a crop in a subsequent year if more deep tillage is done and they are turned back up to the surface. If no tillage is not done, it will take longer for the microbes to break them down and thus prolong the life of the sclerocia to infect that field.”

There are biological products available to aid in the control of white mold. “There is a product called Contans. Contans contains another fungus that is able to parasitize and infect the sclerocia and break them down,” said Webster. “A lot of the biologicals need incorporated in the soil so that they can survive. The soil surface is rough environment for a lot of the pathogens. The sclerocia survive because of the hard structure they have. It allows them to persist. This makes for a difficult situation in a traditional no-till system.”

The white mold development information is from a program conducted by Lee Beeres, Assistant Professor and OSU Extension Educator, Trumble County along with Dr. Horacio Lopez-Nicora, Assistant Professor, Plant Pathologist and Nematologist at The Ohio State University, and Dr. Wade Webster, Assistant Professor, Soybean Pathology, North Dakota State University.

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