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Rains cut Mississippi soybean yields

Many soybean farmers across Mississippi are seeing great yields cut in half or more as heavy rains are causing seed deterioration before the crop is harvested.

Group 4 soybean varieties that were ready for harvest are being hit the hardest from a week of rains that came near mid-August. Specialists have identified the disease that is deteriorating the seed in the pods as phomopsis. Yield losses are estimated as high as 50 to 60 percent in some fields.

“This is an organism that causes seed rot,” said Alan Blaine, soybean specialist with Mississippi State University's Extension Service. “Like aflatoxin in corn, it just has to have the right environmental conditions to express itself.”

Those conditions came along when significant rains fell on mature varieties in August.

“You see white, moldy growth and the seed begins to wrinkle up and deteriorate to nothing,” Blaine said. “It results in tremendously low weights, depending on the degree of the disease.”

Phomopsis is being found in the hills' crop, but it is not as bad as in the Delta since these beans are maturing later than the Delta crop. The disease works quickly and struck after the crop was mature enough to discontinue fungicide applications.

“I don't think this will be a historical problem,” Blaine said. “The best thing that could happen now is happening, and that is the sun has come out and it's started drying up.”

Blaine said stinkbugs appear to have contributed to the problem, but are not its cause.

“I think where this problem is worse is where we have let stinkbugs go unchecked,” Blaine said. “We're seeing some areas of fields worse hit with this disease than others, and they seem to be the areas where higher populations of stinkbugs were present.”

Mike Griffin farms 800 acres of soybeans in Cleveland, Miss. He has 100 acres of the Group 4 soybeans and has phomopsis throughout this field.

“This is our first year to grow Group 4-maturing beans, and we just happened to get in the window of opportunity for a disease we haven't seen much of in the last few years,” Griffin said.

His other soybeans are unaffected by the disease, but those hit are shriveling in the pod or turning to chalk inside the bean hull.

“It seems like every time we kind of get things figured out like we can make a good living, nature throws another curve,” Griffin said.

Blaine encouraged growers to examine their fields for signs of the disease, which include speckling on the pods that turns to big brown or black spots on the outer portion of the pod wall.

Bonnie Coblentz writes for Mississippi State University Ag Communications.

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