Arkansas dodged the bullet of Asian soybean rust in 2005, but University of Arkansas Division of Agriculture scientists aren’t letting their guard down for 2006.

To meet the threat of soybean rust, the Division of Agriculture established the Asian Soybean Rust Working Group, a coalition of scientists working in cooperation with the USDA Animal and Plant Health Inspection Service, the Arkansas State Plant Board, soybean producers and industries.

The working group is attacking the problem along multiple avenues to protect the state’s soybean crop, said plant pathologist Rick Cartwright.

Plant pathologist John Rupe is part of the Asian Soybean Rust Working Group, a coalition of University of Arkansas Division of Agriculture scientists working in cooperation with the USDA Animal and Plant Health inspection Service, The Arkansas State Plant Board, soybean producers and industries to minimize the risk of soybean rust in Arkansas.

Soybean rust is caused by a fast-moving fungus that infects the leaves of soybeans and a few other plants and, if not controlled, can severely reduce yields, said plant pathologist John Rupe.

Because it requires a living host, Asian soybean rust can’t survive over winter in Arkansas, Rupe said. “It has a wide range of hosts, including kudzu, but all its hosts lose their leaves during the winter.”

That means soybean rust has to over-winter in warmer climates and blow in on the wind, Rupe said. In 2004, rust arrived in Arkansas on the winds of hurricane Ivan, but too late to affect the soybean crop. In 2005, it was found mostly in the panhandle of Florida and the southern areas of Georgia, Alabama and Mississippi. It also was found very late in the season in some kudzu plants in Kentucky and Texas.

Much of the working group’s effort is directed at early detection. Rupe said sentinel plots are planted about a month earlier than the soybean crop.

“Rust is difficult to detect in its early stages,” Rupe said. “It likely starts off slowly in the lower leaves where it’s difficult to see, then really takes off during the reproductive stage, the most critical time for establishing yield. Early planting of the sentinel plots gives us about a month’s head start to apply fungicides and prevent serious damage to the crop.”

Samples from the sentinel plots are inspected in Division of Agriculture labs in Fayetteville, Lonoke, Hope and Monticello, said soybean agronomist Chris Tingle.

Rupe said spore traps are also being tested as a means of early detection.

“Collectors send us sample slides from spore traps throughout the South,” he said. “We read those slides for spores that look like soybean rust, and that can give us clues about where to look for it and possibly find it early.

“In South America, spore traps work really well, even detecting rust before the sentinel plots,” Rupe said.
 
Division scientists are looking for other means of protecting Arkansas soybeans, Rupe said.

“We’re looking for soybean varieties that exhibit resistance, which can be developed into improved varieties,” Rupe said. “We’re also conducting basic fungicide research to determine the best timing for application and to determine how late plants can be treated effectively after infection begins.”

Another avenue of research uses genetic tests on rainwater to see if rust DNA can be detected upon arrival.

“Storms are the means by which soybean rust spores move from one area to another,” Rupe said. “Then it spreads locally on the wind.”

Tingle said all research and detection findings are reported weekly to the USDA database. “Producers can go to the USDA soybean rust Web site to monitor progress of soybean rust scouting and detection by county.”