LITTLE ROCK, Ark. -- Leaf rust, a serious disease of wheat, has begun showing up in the 680,000-acre Arkansas wheat crop, according to Jason Kelley, wheat specialist with the University of Arkansas Cooperative Extension Service.
“It’s not serious yet, but we want to get the word out to farmers to be on the lookout. In the next week or two, it could really take off.”
Kelley said the spores that cause the disease probably rode winds that blew in from Texas and Louisiana.
“This week, we’ve seen it from Lafayette County to Craighead County. It’s unusual that we’re seeing it all of a sudden over that great a distance. This disease likes wetter weather and warmer temperatures.”
He and other university agriculture experts have issued a leaf rust alert to farmers in the university’s weekly Arkansas Wheat newsletter.
“This is the first time I’ve seen it in March,” said Rick Cartwright, Extension plant pathologist. “It’s our belief that leaf rust is likely statewide, although officially confirmed only as far north as Craighead County.”
Cartwright's advice is for farmers to watch and wait before treating the disease with a fungicide. If you need more information on how to scout for the disease and how to identify it, contact your county Extension agent.
“The closer we get to the booting development stage before treating, the better, since most growers can only afford one fungicide application,” he said.
Cartwright said all of the fungicides registered on wheat in Arkansas are effective in controlling leaf rust, but timing is important, especially this early.
Treating too early can lead to a loss of control late in the season when the fungicide effectiveness plays out, he said. Treating too late means loss of yield potential that cannot be salvaged.
Kelley said the flag leaf, the last leaf on the plant, is “the one we want to protect with the fungicide. Treating too early can leave the flag leaf unprotected later.
“Current conditions do not favor rapid development of leaf rust, so we will hopefully have a couple of weeks before decisions need to be made. We’ll know more next week, and we’ll report it in our newsletter.” The newsletter is available to farmers by signing onto the Web at Arkansas Wheat Newsletter. 
The wheat specialist noted that moderate to high levels of leaf rust have been reported in southwest Louisiana, and treatments have been made.
Kelley said dry weather will help slow the spread of the disease. He said some varieties are more tolerant of the disease than others. The more resistant varieties may not require treatment with fungicides if the disease becomes an epidemic.
Farmers need to monitor their fields on a regular basis to determine if leaf rust is present.
Meanwhile, Kelley said, stripe rust, a more aggressive form of rust, has been found in one Lafayette County wheat field. Arkansas farmers should be concerned about the potential for that disease to infect their crops.
Lamar James is an Extension communications specialist with the University of Arkansas.