BLACKVILLE — Soybean rust has been found in another three South Carolina counties, taking the number so far this year where the disease has been detected to nine counties.

Most recently rust was found in Colleton, Horry and Orangeburg counties.

Rust was found on two of 50 leaves collected at a site in Colleton County. The first leaf had a cluster of 10 to 15 pustules and the second leaf had two small, very young pustules.
Rust also was found on two of 50 leaves collected at a site in Horry County. Both leaves had clusters of five to 10 young pustules.
And rust was found on 10 of 50 leaves collected at a site in Orangeburg County. The 10 leaves had 10 pustules with 25 young pustules each.  
Rust has now been found in Bamberg, Barnwell, Berkeley, Calhoun, Colleton, Dorchester, Hampton, Horry and Orangeburg counties.

This late-season spread of rust is not a threat to the state’s soybean crop as all the affected fields are in the later stages of maturity, said John Mueller, Clemson University extension soybean pathologist at the Edisto Research and Education Center.

“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 very latest maturing soybeans now,” Mueller said.

However, the weather forecast for the coming week is favorable for rust to develop on late maturing soybean crops, Mueller said.

Crops with seeds in the growth stage with good moisture and yield potential could be sprayed with a Folic-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.