Asian soybean rust was confirmed Aug. 7 on leaves taken from Group IV soybeans growing in an industry research field near Chula in Tift County.

A small leaf sample (<10 leaflets) was submitted to the University of Georgia diagnostic clinic, and rust was confirmed. The Tift County find makes six counties in south central Georgia reporting infections.

Tift becomes the 29th county in the U.S. with soybean rust and the northernmost in Georgia this year.

The positive counties are Brooks, Decatur, Miller and Tift, with Grady and Thomas no longer red on the USDA map after infected plants were destroyed and no more rust found. It is the ninth U.S. county in five states with rust on this season's soybeans.

Tift County is the site of the University of Georgia’s Tifton campus and a center for row crop research, including soybeans. By comparison, rust was first confirmed at the Tifton campus last year on July 15.

University of Georgia pathologists say although Asian soybean rust has been confirmed on kudzu in Miller and Brooks counties and on soybean research plots in Brooks and Decatur counties, it has really not spread much at all this year, likely due to hot and dry weather.

University of Georgia Plant Pathologist Bob Kemerait says, "Many growers may choose to wait to apply the fungicide application until we are able to document rust spreading in our sentinel plots and research plots. For example, though rust was found on soybean plants in Attapulgus, Decatur County (1 leaf of 100) on July 3, we have not found the rust again. We have also not found rust in sentinel plots in Moultrie (SunBelt Expo) or elsewhere.”

To the west, in Alabama, rust was detected over-wintering in kudzu as far north as Montgomery county in the central part of the state, but has not been reported in soybeans in the state.

To the south, in Florida, rust has been found in both sentinel plots and commercial counties in northwest Florida. Movement has been sporadic at best and researchers have not recommended spraying for soybean rust, unless yield potential of beans warrants.

To the north in South Carolina, spores were found in June, but no rust has been detected in the state and soybean specialist John Mueller says no recommendations have been made for growers to spray beans for rust.

A recent find in southwest Mississippi has not spread from the site in Jackson County. Hot, dry weather throughout most of Mississippi has not been conducive to spread of rust and Extension specialists say soybeans in the Delta and northern Mississippi are not threatened by rust at this time.

Though some scattered rainfall in late July in south and central Georgia brought some relief from the drought, intense heat in August has offset most of the gains. Throughout the southern tier of states, where rust begins its move northward, extended hot, dry weather has severely limited its movement.

e-mail: rroberson@farmpress.com