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Corn+Soybean Digest

Soybean rust in state, soybean crop still OK

Despite the arrival of rust in the state, Mississippi’s soybean crop needs only a couple of well-timed rains to finish off what could be one of the best crops.

On July 18, rust was confirmed in a sentinel plot of soybeans in George County. Mississippi State University Extension Service plant pathologist Billy Moore collected 15 leaves from this quarter-acre plot that were exhibiting vague symptoms of rust. The fungus was found on one leaf.

“I pull samples all the time based on symptoms,” Moore says. “Often it’s just herbicide damage or something. This time, it happened to be rust.”

Extension soybean specialist Alan Blaine compared this to “finding half a needle in a haystack.” He said this sentinel plot was destroyed July 19 in cooperation with the Mississippi Department of Agriculture and Commerce.

The age of most of Mississippi’s soybean crop will help prevent possible damage from rust. Blaine said the crop is the earliest in the nation, and recent rains have made it exhibit tremendous potential. By Aug. 1, half the crop should be finished, and the next 25% by mid-August.

After a crop has reached maturity, events such as disease or drought do not reduce yield nearly as much as they could earlier in the growing season.

Blaine says once rust becomes established in Mississippi, soybean producers will have to make fungicides a regular part of their management practices or consider growing another crop.

“We know that the correct fungicide applied at the right time can make us money, regardless of rust,” Blaine says. “We left a lot of money laying on the table this year because we’ve been so focused on rust that many failed to think about any other disease.”

Though producers once saw the use of fungicides as a luxury they could not afford, it will become a necessity. Timing of the applications is critical.

The U.S. Department of Agriculture offers tips on good farming practices and fungicide guidelines in the battle against rust. Information is available online at

The Soybean Promotion Board continues to fund Extension’s twice-a-week monitoring of the sentinel plots scattered across the state and several other fields to give producers the information they need to battle the disease when it arrives in their areas.

“One occurrence of rust has been found in the state,” Blaine says. “Every soybean producer needs to watch how far it spreads, then make their own treatment decisions based on such things as their location, the crop’s maturity group, when they planted, and whether it’s a dry land or irrigated field.”

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