Beat the Disease Before It Beats Down Yields

Feb 15, 2023

White mold is the most prevalent disease on soybeans in east-central MN and westernWI.
This is the third article in a series on farm planning focused on three critical areas of crop management: decision making, crop protection, and fungicides/insecticides.
Crop diseases are typically best controlled before they are evident – before the crop is damaged. But how do you address something you can’t see?
Consider history. And plan ahead.
Don Lamker, Federated ag sales rep for Ogilvie and Rush City, said, “Ask yourself, ‘What’s the field’s history? Is there a history of white mold [for example] in certain areas?’” Once you have identified historical problems, you can address them with current solutions.
First off, consider the seed varieties that are resistant to the disease. In this geography, Lamker noted, white mold is the biggest issue. And, as with many diseases, by the time you see white mold, “it’s too late to get any decent control.” Federated recommends several seed varieties that rate their white mold resistance, which can help mitigate or minimize the issue.
While crop rotation is an important tool in the fight against crop disease, it isn’t the answer in and of itself. White mold, again the prevailing example, remains in the soil for a long time. “Going away from soybeans for several years can help,” said Lamker, but “white mold has the ability to wait it out until the conditions are right for it to grow.”
“Planting resistant varieties is the better tool,” said Lamker, since “there are enough diseases that we never actually see.” Applying a fungicide is good crop management.
A new concern for corn in recent years is tar spot, a disease that is “moving west and north,” said Lamker. It wasn’t in Federated’s area five years ago, but it’s doing damage and affecting yields in corn now.
The window for fungicide application is relatively small, especially for white mold on soybeans. Fungicides can be tank mixed with post-emerge herbicides and applied at the R3-R4 stage. On corn, “it’s typically a little later, but corn height comes into play,” said Lamker. Scouting is the best option for timing on corn, since corn height affects the ability to spray (short of aerial application).
Miravis Neo® is the main product Federated recommends because of its broad-spectrum control; its three active ingredients make it less likely for disease resistance to develop. See this fact sheet for further information: Miravis Neo on corn, Miravis Neo on soybeans.
Planning for potential insecticides comes right behind fungicide planning. This geography can see aphids (in a dry year) and spider mites (in a wet year). Both insects can be treated when they appear – which highlights the importance of field scouting.
Alfalfa weevils are another concern for hay/grass growers; they do damage to the leaves as weevils, and at the root level while still in worm stage. Worms feed on the roots between cuttings, causing subsequent crops to be weakened. “We typically spray for weevils between first and second cuttings,” said Lamker, but digging down to check for the worms prior to a cutting provides the opportunity to spray even earlier.
Talk to your Federated Agronomist about 2023 farm plans soon. Look back at the other articles in this series as well: pre-season decision-making, and crop protection planning.

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