A milder winter in parts of the South may be to blame for the early start to Asian soybean rust. In some parts, this is the earliest recorded findings of the fungus.
“Soybean rust has now been confirmed and is actively sporulating in Alabama, Florida, Georgia and Louisiana,” said Don Hershman, Extension Plant Pathologist, University of Kentucky. “Most sightings are on kudzu except for Louisiana where the disease has been seen on kudzu and volunteer soybean.
“Once we hit March 1, the chances of a hard spring freeze cold enough to take out soybean rust, are very low. This is the perhaps the most SBR that has existed this early in the season. Assuming no hard freeze from here on out, the weather in April and early May in the deep South will determine our [Kentucky’s] risk later in the summer.”
Louisiana discovered the disease on kudzu Jan. 2, which confirmed that Asian soybean rust could overwinter in the state.
“Finding the rust is not really new following mild winters, but finding it in eight parishes mainly along the coast, and also finding it in 6-inch high volunteer soybeans, is new,” said LSU AgCenter plant pathologist Clayton Hollier.
Although soybean rust has not been an issue for soybean-growing areas in the Midwest, the South and Mid-South have had to manage the disease’s spread. With this year’s mild winter, overwintering of the fungus and more spores than usual this early in the season, farmers are being urged to be vigilant.
Hollier said that while farmers are cautioned to be vigilant, they should not panic. He said this early development of the disease would be historic for its early start, but actually it just means that growers may have act earlier to control the fungus this year.
In the past, freezing temperatures have delayed the emergence of the disease to the point that the soybean crop was far enough along in development to not be affected much by it.
“The chance of the disease affecting soybeans early this year can all be changed by a few nights or days with temperatures in the lower 20s,” Hollier said.“The reason we haven’t had an epidemic here is because it takes time to build up after a freeze has killed it back. By the time it builds back up, we’re actually late in the growing season.”