WISCONSIN DELLS — From 2010 to 2014, white mold and sudden death syndrome made the top 10 list of the most destructive diseases in soybeans across the U.S. In Wisconsin, the two diseases ranked even higher — second and third, respectively, behind soybean cyst nematode.
Fortunately, there are things that soybean farmers can do to limit the chance of infection and if crops become infected, remedy the issue, said Damon Smith, an associate professor and field crops Extension pathologist in UW-Madison’s Department of Plant Pathology, during his session at the Corn/Soy Expo Jan. 31.
When it comes to white mold, it’s important for farmers to properly clean their combines as the fungus acts like a weed seed, capable of being transferred from field to field rather easily. Plants are most susceptible to the disease during the crop’s flowering stage, when spores attach and cause damage that typically isn’t seen until two or three weeks after the initial infection.
“White mold is a high-yield disease,” Smith said, adding that a truly integrated strategy and multi-pronged approach is needed to manage it.
Some research has been conducted at UW-Madison in regards to white mold-resistant varieties, although nothing is 100 percent immune to the disease. Smith recommended farmers study the yield and white mold score before selecting a variety and consider the environments and fungal populations on their operations as they can differ from field to field.
In the future, Smith hopes to be more helpful in giving farmers the ability to know which varieties have resistance so they can modify their management practices. Fungicide is a good tool for susceptible varieties, but he argued that it’s not good for a soybean variety to respond to a fungicide; he’d rather the variety have some resistance instead.
From 2009 to 2016, fungicide trials were conducted in Illinois, Iowa, Michigan, New Jersey, Minnesota and Wisconsin, with different products, rates and timings used and evaluated in regards to white mold disease and yield. Through these trials, researchers were able to determine that even with the best ingredients in the fungicide products, they only saw about a 20 percent reduction in disease, Smith said.
However, the trials solidified the importance of the timing of a fungicide application, which plays an important role in maximizing disease reduction, with Smith providing information on two free tools that farmers can use to help improve the use and efficiency of fungicides.
“Sporebuster” is a free fungicide calculator app for Android and iPhones, used to determine break-even profitability and average net gain when using 10 common fungicide programs.
“Sporecaster” is another free cellphone application that uses user inputs, GPS, math and modeling to give farmers a warning if the probability of mushroom presence is high. Since its launch in May 2018, this app has been downloaded more than 1,600 times with 250 active users during the peak season.
“It can help optimize sprays as well as tell you when to spray,” Smith said.
Like many areas of research, there is always more work to be done. Integrated management trials will continue in Wisconsin, Illinois, Iowa, Minnesota and Michigan in 2019, with data collection and analysis focused on row spacing, planting populations and fungicide applications to manage white mold.
Research also continues at the UW with sudden death syndrome in soybeans, a root rot disease that affects plants early in the season.
In 2018, the southern third of the state had real issues with sudden death syndrome, Smith said, as the weather played a significant role in its emergence. He recommended farmers carefully inspect plants, pulling a few out of the ground to check on their roots as leaf discoloration later in the season could mimic other diseases.
He also recommended several management practices that could help protect soybeans from this disease, including selecting varieties that are high yielding, planting at the right time, not delaying planting and managing soil compaction as the disease tends to show up in heavily compacted areas first.
“We are starting to see a few very good rated sudden death syndrome-resistant cultivars,” he added.
Research from the UW is also suggesing that an ILeVO seed treatment could be helpful in fields that have a history of sudden death syndrome.
For more information, visit badgercropdoc.com, a UW-Madison and UW-Extension website offering the latest in research and outreach pertaining to field crop diseases and their management.