As season nears end, don’t drop your guard on soybean rust

• By Dr. Lindsey Thiessen •

Soybean rust
Soybean rust — photo courtesy North Carolina State University

Many of the soybeans in North Carolina are past the critical growth stages for impact by soybean rust, but there may be a few late-planted, later-maturing fields that could be affected by the disease.

Since Hurricane Florence passed through, several new rust confirmations have been reported. Soybean rust has been identified in six counties in Georgia, four counties in Alabama, two counties in Florida, two counties in Mississippi, one parish in Louisiana, and, just recently, one county in South Carolina.

The South Carolina report was from Bamberg County, which is approximately 140 miles from Charlotte, 345 miles from Elizabeth City, 175 miles from Fayetteville, 210 miles from Murphy, 220 miles from Raleigh, 275 miles from Washington, 180 miles from Wilmington, and 210 miles from Winston-Salem.

We recommend spraying a fungicide to prevent infection soybean rust is confirmed on soybeans within 100 miles of your field, and the soybeans are between first bloom and stage R5 (early seed development). We do not recommend spraying a fungicide to prevent soybean rust if the soybeans are at stage R5 (early seed development) or beyond.

By the time soybeans reach stage R6 (full sized beans in a pod on one of the top four nodes), they will typically lose all their leaves, so rust no longer has the potential to cause economic damage.

Find the current status of rust in the continental United States.

Dr. Lindsey Thiessen is an assistant professor and Extension Specialist in the Entomology & Plant Pathology Department with North Carolina State University. Email her at ldthiess@ncsu.edu.

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