Soybean disease reported in Midwest U.S.

Recent reports of soybean disease throughout the Midwest are likely to cause economic losses for some farmers this year, according to plant pathologist Carl Bradley of the University of Illinois.

In a recent article, Bradley specifically described the signs of two different diseases, sudden death syndrome (SDS) and Sclerotinia stem rot (white mold), both of which are caused by weather related conditions and are appearing not only in Illinois but also throughout states including Iowa, Michigan, Minnesota, South Dakota, and others.

The symptoms of SDS currently being observed include interveinal chlorosis and necrosis of the leaves, which is described as the veins remaining green, while the tissues between the veins turn yellow and then brown. Similar to another disease, brown stem rot, SDS does not affect soybean stems as you would see with brown stem rot.

“Although the foliar symptoms of SDS are now being observed, infection by the SDS fungus occurred during the seedling stage, not long after planting. The symptoms that are now being observed are the effect of toxins that the SDS pathogen produces that are phytotoxic,” Bradley said.

A mixture of cool and wet weather after planting combined with rain fall later in the growing season makes conditions favorable for SDS. White mold is also a weather-related disease resulting from cooler and wetter than normal conditions after soybean plants began to flower. Once white mold signs and symptoms are detected however, fungicide applications generally do not work as the damage has already been done.

Bradley noted that growers with severe levels of white mold may encounter some discounts at the elevator this year for high levels of foreign matter. “Some sclerotia (dark survival structures produced by the white mold fungus Sclerotinia sclerotiorum) that are formed on plants may be similar in size to the seed, and will make their way to the hopper and eventually the elevator, where discounts may be received,” he said.

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