BLACKVILLE — Soybean rust has been found in three more South Carolina counties: Bamberg, Calhoun and Hampton.

Rust was found on two of 50 leaves collected at a site in Bamberg County. The first leaf had a cluster of 10 to 15 pustules and the second leaf had two small, young pustules.

Rust was found on 10 of 50 leaves collected at a site in Calhoun County. The 10 leaves had five to 10 young pustules.

Rust also was found on 17 of 50 leaves collected from a site in Hampton County. Ten of the leaves had less than 10 pustules.

“These were very young pustules, the youngest I have ever seen, just barely producing spores,” said John Mueller, Clemson University extension soybean pathologist at the Edisto Research and Education Center 

The other seven leaves from Hampton County had 1 percent to 3 percent of their surface areas with rust, Mueller said.  

So far this year rust has been detected in Bamberg, Barnwell, Berkeley, Calhoun, Dorchester and Hampton counties.

This late-season spread of rust is not a threat to soybean crops due to the maturity of the affected fields, Mueller said. However, the weather could affect late-maturing crops.

“We may have some premature defoliation in a few fields that were not treated with a fungicide, but it is too late for this to hurt all but the latest maturing soybeans,” he said.

Crops with seeds in the growth stage with good moisture and yield potential could be sprayed with a Folicur-type product just for the rust, Mueller said. More advanced crops are too late for a fungicide spray, but at such a stage should not see much yield loss, he said.

Soybean rust — yellowish in appearance on plant leaves — is a disease that causes early maturation and severe loss of yield through premature foliation and decreased seed weight.