Soyarust, which can slash crop yields by up to 80 percent, was discovered in Craven, Duplin and Pender counties. The USDA did not say what type of plant the fungus was found on.
Even if more cases are found this year, most of the US soyabean crop has been harvested so the fungus will not affect yields, according to the USDA.
On Monday, the disease was found for the first time this year in Louisiana. During the past six days, 23 US counties, mostly in North and South Carolina, have reported new cases. Rust also has been found in Alabama, Georgia, Mississippi and Florida this year, all states that grow a relatively small amount of soyabeans.
Rust was first found in the continental United States last November after spores were blown into the US Gulf Coast by a hurricane. The fungus thrives in warm, humid weather under cloudy skies, and is spread by the wind.