White mold on soybean. (Iowa State University/Daren Mueller)
WEST LAFAYETTE, Ind. - A group of university researchers, in conjunction with the North Central Soybean Research Program (NCSRP), have created a podcast to help farmers deal with white mold, a disease of soybeans.
"Management of White Mold in Soybean" is a seven-part podcast series available for free download on iTunes. It covers topics such as how to identify white mold, estimating yield loss, impact of irrigation on disease development, foliar fungicides, understanding risk of white mold in a growing season, biological control and guidelines for an overall management plan.
The podcasts are especially relevant as most soybeans are now planted and emerging, and farmers need to be aware of white mold, said Kiersten Wise, Purdue Extension plant pathologist and podcast co-creator.
White mold, also called Sclerotinia stem rot, is caused by the fungus Sclerotinia sclerotiorum and can affect plant growth and ultimately yield and profits.
"White mold isn't a problem every year in Indiana, but when it is present, it can cause significant yield loss," Wise said. "Growers who have had white mold problems in the past should be prepared for the disease, since the fungus that causes white mold survives in the soil for a very long time."
This disease thrives in cool, wet conditions and under a dense foliar canopy. Early planting, narrow row width, high plant populations and high soil fertility all can contribute to more dense canopies, and increase the risk of disease development.
White mold on soybean. (Purdue Botany and Plant Pathology/Kiersten Wise)
"The fungus that causes white mold infects soybeans as they're starting to flower in growth stage R1," she said. "If cool, wet weather persists during flowering, a fungicide application might be necessary to suppress the disease."
Wise said there are several fungicides that are available for use on white mold, but not all commonly marketed fungicides are effective against the disease. Growers should contact Extension personnel to determine which fungicides are recommended for use on white mold.
Management of white mold can be tricky because once farmers find evidence of the disease in the field, it might be too late to manage it that year. But identifying the disease can help future crops.
Wise said white mold is an easy plant disease to identify.
"If you suspect that you have white mold in your soybeans, walk into a field and pull back the canopy and look at the lower stems," she said. "If it looks like little bits of cotton are stuck to the lower stems, that's a good indication that you have white mold."
Recordkeeping and knowledge of field history are important parts of controlling white mold.
"The next time that field goes into soybeans, you want to choose a variety that is less susceptible to white mold and make sure that you're planting at recommended seeding rates," Wise said. "The higher the seed population, the more conducive the environment will be for white mold to develop."
Incidences of white mold vary from year to year, but Wise said Indiana had major occurrences in 2009 and 2011.
A PDF text version of "Management of White Mold in Soybean" to accompany the podcasts is available for free download at http://planthealth.info/pdf_docs/WhiteMold_NCSRP.pdf.
The North Central Soybean Research Program is a farmer-led organization funded by checkoff dollars. It includes researchers in 12 states: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota and Wisconsin.