Soybean South

Soybean Rust Update

Where’s the rust? Asian soybean rust was found to survive Georgia’s winter on kudzu in at least four counties in southern Georgia and also in northern Florida and Alabama. However, no new rust has been found in Georgia since mid-March and none has been found spreading to new kudzu in our state.

Given the early finds of Asian soybean rust in Georgia, we predicted that the disease would have already become well-established on new-growth kudzu. To date, (May 16), this has not happened.

The question becomes, “Why not?”

‘La Niña’ weather patterns
The most likely reason that rust has not yet spread in the state has to do with the “La Niña” weather patterns this spring that included conditions that are warmer and drier than normal.

Given that scarce rainfall fell in the state during March and April, conditions were unfavorable for the spread of the rust disease. (Free moisture is critical for the germination and infection of rust spores).

Some may ask “Are we out of danger from rust now?” because the disease has been slow to spread. The answer is certainly “NO!” We have a long way to go before our crop reaches the relative safety of the R6 growth stage.

In fact, we have begun to receive more rainfall in the first two weeks of May.

Disease spreads on Florida kudzu
University of Georgia climatologist Dr. Joel Paz has reported that “La Niña” is nearly over, and we can expect more typical rainfall patterns in the future.

Also, researchers at the University of Florida have just reported the likely first-find of the disease spreading on kudzu in the northern part of the state. They attribute this development to recent rainfall.

Soybean growers in Georgia should be assured that the Soybean Team at the University of Georgia has an ongoing monitoring program for early detection of (Asian) soybean rust.

When rust is detected, growers will be quickly notified through the (University of Georgia) Extension service.

National rust commentary
As of May 18 of this year, the USDA’s National Soybean Rust Commentary says scouting continues on kudzu patches from Florida northward to southern Illinois, and westward to Texas and Nebraska.

Many of the soybean sentinel plots have been planted throughout the country with the most advanced ones in the South starting to fill pods.

Currently, there are no reports of rust on newly planted soybeans in 2006, including volunteer plants. Rust has been confirmed in five counties in Alabama, 11 in Florida, four in Georgia and one in Texas.

Recent rains in the South may provide the right conditions for increased spread of the fungus to new locations, especially in the South. To keep up with the latest rust reports, please visit the USDA’s Web site at

Editor’s note: The soybean rust update from the University of Georgia Cooperative Extension Service is by Bob Kemerait, Extension plant pathologist and Layla Sconyers, research post-doc, plant pathology. For even more soybean info, please visit The National Soybean Rust Commentary is provided by the USDA.