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Wheat yield potential favorable, but disease problems loom
Arkansas
The Arkansas Wheat crop appears to have good yield potential, and the price is favorable. The crop is growing rapidly and is on schedule for harvest in June.
Meanwhile, the Arkansas Agricultural Statistics Service has revised its estimate of the size of the crop from 680,000 acres to 720,000 acres.
But it's not all good news. Potential disease problems could threaten yields and profits, according to Dr. Jason Kelley, Wheat specialist with the University of Arkansas Cooperative Extension Service.
He said four Wheat diseases have shown up in the crop in the last few weeks, and some farmers have begun spraying fungicides. The diseases being seen are stripe rust, leaf rust, powdery mildew and barley yellow dwarf virus.
"A few weeks ago, leaf rust, a warm weather disease, began showing up. But then cooler temperatures moved in and held the leaf rust in check. Cooler temperatures allowed stripe rust, a cool weather disease, to advance.
"Now, it's warming up so that will favor the spread of leaf rust."
Kelley said Dwayne Beaty and Trey Reaper, extension verification program coordinators, have found stripe rust in verification fields in Woodruff and Lawrence counties.
Stripe rust, which is more aggressive than leaf rust, has the greatest potential for yield losses, Kelley said.
"If a farmer has a susceptible variety, stripe rust can cause a 50 percent or greater yield reduction. If you've got large spots of stripe rust, go ahead and spray," Kelley advised
Complicating matters is the fact that powdery mildew, a yield-robbing disease, is showing up in several places around the state.
Kelley said, "Many varieties in university plots in Lafayette County have powdery mildew, and it's severe in parts of Jackson County.
"Most of the time, farmers don't have to spray for it. But everyone is saying it's worse this year than in recent years. Several fields have been sprayed."
Fungicides are costly; an application costs about $15 an acre. "At $4 a bushel, you'll cover your costs, if spraying can guarantee another three or four bushels an acre," Kelley noted.
Kelley said motorists driving near Wheat fields can see the results of another disease, barley yellow dwarf virus. The disease is transmitted by aphids in the Wheat during the fall and winter. Symptoms begin showing up in the spring.
"Usually what you'll see is streaked or spotty yellow patches in the field," the extension specialist said. "If symptoms are really bad, the Wheat will be stunted which affects yields.
"What we're seeing now is yellow tips on the leaves. In most cases, the Wheat is not stunted, so we're not expecting much in the way of yield reductions."
Kelley said mild, dry fall weather caused the aphids to flourish and transmit the disease. He said university entomologists and plant pathologists had looked at the situation in the fall and had predicted disease problems.
"There's nothing farmers can do about it. The damage, if any, was done in the fall or winter months. It can reduce yields, but most of the fields that are affected probably have a 10 percent or less reduction in yields."
Kelley said disease scouting can pay off for farmers.
Extension verification coordinators scout participating farmers' fields weekly looking for problems. He said timely spraying for diseases in these fields pay for themselves, adding that the verification fields routinely produce 10 to 15 bushels an acre more than the statewide average yield.
For more information about Wheat diseases or the verification program, contact your county extension agent. The Cooperative Extension Service is a part of the U of A Division of Agriculture.
Date: 5/6/04
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