Soyabean rust was found in a 16th county in Alabama, but the US Agriculture Department said on Wednesday that fall weather was slowing the spread of the highly-contagious fungus.
USDA said five soyabean rust lesions were observed on one leaf taken from a sample on a harvested research plot in Macon County, Alabama.
Favourable weather for further spreading of the disease is expected on Wednesday along the coastal areas of the Carolinas, Georgia, and the Florida peninsula. The focus is expected to shift to only southern Florida on Thursday.
"By Friday favourable disease weather is not predicted over the soyabean regions," USDA said on its rust-monitoring Web site.