White mold has been held off… so far

Progression on the farmland, around our area, is slow but steady. Soybeans have made tremendous gains, with 91 percent of the Wisconsin soybean crop setting pods, that is only 3 percent less than it was last year. Seventy-five percent of the crop is rated “good” to “excellent,” which stands alone at the top of major cash grain states (Minnesota 66 percent, Iowa 63 percent).

One obvious reason for this has been our ‘just in time’ rain events we have been having lately. In a previous article, I talked about the low amount of rainfall we have had, but since then August has really picked up the pace. We are comparative to a 15 year average. Once that rain began to feed the ‘beans they really took off.

Another thing that has been noticeable, particularly with soybeans in our area, is the lack of white mold. In case this is something that you are not familiar with, white mold is a fungal infection that can not only reduce yield of the soybean plant, but kill it altogether. It begins as a mushroom, a tiny thing that looks like a tan colored dinner plate, and about the size of a BB. When conditions are right it emerges from a black chunk called sclerotia.

Think of the sclerotia as a garden pot with seeds in it, or perhaps a ticking time bomb; it acts as a vessel for the mushrooms to bloom from when the conditions are just right. Those conditions are the same like what all mushrooms want: a cool, wet place. Once it comes out of the ground it releases spores up, into the air, and hope to land on a place they can infect, which happens to be the flower peddle of a soybean plant. Its gentle flower is the weak spot in its armor. From there it creates a white, yucky ‘fuzz’ around the area it infected and begins to develop sclerotia inside the stem of the soybean, waiting for the plant to break down, fall to the ground and continue the cycle again.

Massive infections of white mold have the capability of reducing yields 35-60 percent, but a minor amount can be as little as 1-10 percent. It also can be extremely persistent. White mold can survive without a host plant in a field close to a decade.

With the very hot, dry conditions the white mold mushrooms were held at-bay. The soybeans stayed smaller, didn’t canopy immediately, which left a lot of field surface exposed to direct sunlight. This kept the sclerotia from sprouting mushrooms, because it was too hot. But once we started getting rain and the soybeans canopied, mushrooms emerged just recently this season. In our field walks we are beginning to see minor infections (a few plants, hereand- there) in the upper part of the plant, instead of the lower part of the plant. If the mushrooms appeared earlier, the bottom flowers would have been infected, showing mold on the lower half of the plant. Since the mushrooms showed up later (more than likely late July, early August), the lower flowers were allowed to get pollinated and turn into seed pods. We were cursing the heat and dry weather, but it saved the majority of the soybeans from white mold.

The weather cannot be the only factor, however. Lately more and more farmers have been reducing their seeding populations, adopting wider row spacings (7 to 30 inches), having timely fungicide applications, and adapting their rotations to include small grains, forage, and cover crops to disrupt the corn-soybean only alteration. These approaches cannot eliminate white mold totally, but it does heavily reduce its presence.

If you are curious to find out more about white mold, reach out to my brother, Wade Oehmichen. Through his work at BASF, he has done a lot of work researching it, and is always eager to share his knowledge with someone.

If you want to find it for yourself, next time you are in your field, your neighbor’s field, or perhaps at Tesmer’s Town-And-Country talking to a farmer, look across the field for soybean leaves that look dark brown, as if the plant was set on fire. Take a look down the stem of that plant, and if you see white, puffy, fuzzy growth on green tissue, that means you found white mold. I hope you do not have happy hunting.

THE SOIL

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