Clemson University plant pathologists have found, new and more active soybean rust infections in Calhoun and Orangeburg counties.

Rust infectons were found on 7 of 200 leaves collected at the Calhoun County site on Sept. 1. On at least half of these leaves more than 15 lesions were observed. This is compared to one leaf with one lesion the previous week.

“Our current weather is very favorable for the spread and development of rust and other fungal diseases of soybean,” says Clemson Pathologist John Mueller. The rains received from tropical storm Ernesto last week, along with this week’s predicted afternoon thunderstorms and relatively low temperatures should be favorable for the spread of rust within and between fields, he notes.

The two rust finds are almost in the center of South Carolina’s soybean growing region. Although these are not extensive finds they indicate that rust is present in South Carolina and could be in other fields throughout the state, according to Mueller.

Based on these latest finds, it is appropriate to begin spraying for rust in any field in South Carolina where the yield potential is relatively high and the plants are at or past R3/R4 but not within 10 to 14 days of R6.

A strobilurin should be included in the spray to increase control of diseases other than rust. A combination of a strobilurin and a triazole could also be used.