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Rain makes grain…..and soybean disease

It’s a truism that rain is needed for yields. The bitter irony is that rain, and fog, and dew also drive the growth of the fungal diseases that limit our yields. Here are a few examples of what you can see from the road, and what it looks like up close. Inspect your fields before while they are still green so that you have a better understanding of what cost you yield so that you can make improvements for 2018.

Anderson1This duo of pictures is the Sudden Death Syndrome (SDS) that is flaring up across IN/OH these days. The base of the plant showing discoloration of the woody tissue defines this disease. The initial infection got started back in the spring when the soil was wet. Soybean Cysts Nematodes feeding on the roots allows the fungus to enter the plant. Choose the right genetics with both SDS and SCN protection for 2018 and make sure your seed treatment is the best you can get.

Anderson2Here we have 2 pictures of Sclerotinia White Mold. This disease is often driven by heavy rains when the beans are beginning to flower. The fungus splashes up from the soil and infects the plant through the flowers. Note that in the picture to right you can actually see the white mold growing on the outside of the plant. If you look closely in the white mold you may see the black specks of hardened sclerotia. The sclerotia function as a long term “overwintering” structure for the disease. They can last in the soil for years so that when conditions are right they can infect your soybeans again. Rotating can help minimize this disease, as can reducing populations or moving to a wider row width.

Anderson3Frogeye Leaf Spot has also been prevalent this year. Varietal difference can be quite dramatic under heavy pressure. Good yield potential needs to be matched with key defensive traits. Some of our best soybeans come prepared with the Rcs3 gene for protection from Frogeye Leaf Spot. Additionally, growers who utilize a top-quality fungicide with both curative and preventative properties have been able to manage Frogeye quite well.

Anderson4The dark red lesion at the soil line is characteristic of Rhizoctonia root rot. Infection and seedling blight can occur early in the year. Rhizoctonia prefers warm and wet conditions, but can be problematic even in drier years. Infected, but surviving plants such as this one are more subject to yield and premature death later in the season.

Anderson5These 2 pictures illustrate Septoria Brown Spot. I took them at our Grow More Experience site this year. In the first picture everything looks just fine. But walking into the rows just a few steps shows what’s really going on inside the field – yield is being lost to disease. The field edge got enough wind and sun to dry out and limit disease. Inside the canopy, conditions were plenty moist for Septoria Brown Spot to infect the lower leaves and begin climbing up the plant. In the years before the advent of foliar fungicides I was not concerned about Septoria. In recent years I have come to appreciate just how damaging Septoria Brown Spot can be.

So go ahead and get the combine prepped for harvest, but make a little time to inspect your fields to see what’s going on past the end rows.

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