Update from the Field: Not Mushroom for Fungus
Posted by David Dyson, Agronomist on July 16, 2018
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As the days start to get shorter, our soybeans are starting to flower. Once soybean plants start flowering, they enter the reproductive stage, and the plants can be very susceptible to stress. This stress can come in many forms: drought, insect, weeds, and fungus. In this article, I will describe three different fungi that can cause stress on the soybean plants, potentially reducing yield.
The first fungus I would like to discuss is sudden death syndrome (figure 1). This disease is caused by the fungi Fusarium virguliforme. Sudden death syndrome is a soil-borne fungus that will overwinter and survive on residue. Cool, wet weather in the early vegetative stages of plant growth will promote infection. Wet conditions at flowering, followed by warm dry weather, favor symptom expression. The presence of soybean cyst nematodes can transmit the fungus into the plant. To confirm if the soybean cyst nematode numbers are high, pull a soil sample 12 inches deep in the sudden death area. If the test comes back positive, seed treatments next year are the only viable solution for soybean cyst nematodes and will limit the spread of sudden death syndrome.
Figure 1: This image shows sudden death syndrome, a disease that will always present with interveinal chlorosis. This picture was taken around Walton, IN, in2017.
The second fungus is downy mildew (figure 2). This disease is caused by the fungus Peronospora manshurica and presents as lime-green spots on the upper leaves. Cool, humid weather favors the spread of downy mildew. This disease can wipe out new leaves, leaving the upper canopy devoid of chlorophyll.
Figure 2: This image shows downy mildew. This picture was taken near North Manchester, IN, in 2016.
The third fungus is frogeye leaf spot (figure 3). This disease is caused by the fungus Cercospora sonjina and presents as circular to angular spots, up to 1/4-inch in diameter, that develop on the leaves. Spots have tan centers with a reddish brown or purple outer ring, and premature defoliation may occur. The fungus survives in the soybean residue or infected seeds. Warm, humid weather favors the spread of the disease. Young leaves are more susceptible, so as each leaf layer develops, lesions may be heavier on some leaf layers than others.
Figure 3: This image shows frogeye leaf spot, with lesions that will spread and until there is no green leaf material left. This picture was taken around North Manchester, IN, in 2015
During this transition, the soybean plant expends quite a bit of energy. To replace this energy, we can apply The Andersons’ Sweet ‘N Eezy™ product at .5 gal/ac while going through the field applying fungicides. Sweet ‘N Eezy is The Andersons’ propriety blend of sugar that provides soybean plants with a boost of energy. However, this boost will not last long. I like to use the analogy of burning paper to represent applying sugar to crops. As with burning paper, it will not last for a long time, but it will burn hot for a short time and can produce enough energy to get a bonfire started. Supplying energy with .5 gal/ac of Sweet ‘N Eezy and nutrients with .5 gal/ac of Overpass® SF liquid fertilizer, all while protecting your crop with fungicides, is a solid way to get the full potential out of your soybean crop.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
OverPass is a registered trademark of The Andersons, Inc. Sweet 'N Eezy is a trademark of The Andersons, Inc.
