Mother Nature can't seem to make up her mind. Through mid-April — sandwiched by warmer days — cool, wet spells swept through Arkansas and Mississippi. Reports of stripe rust began popping up in southeast and east-central Arkansas. Now, stripe rust has been found as far north as I-40 in the eastern part of the state. In Mississippi, stripe rust reports have mainly come from the Delta side of the state.
“We put out an alert to county Extension agents, consultants and producers to be on the watch. If they were concerned about their good wheat fields, last week was a good time to start scouting,” says Rick Cartwright, Arkansas Extension plant pathologist.
By early in the second week of April, Cartwright and colleagues had “a lot” of reports of stripe rust in eastern Arkansas.
“There was quite a bit of fungicide going out. Then, starting (April 12 or 13), temperatures have hit 85 degrees to 90 degrees and that slowed the stripe rust down — probably considerably.
“Any time you get high day temperatures and warm nights — which we've had for three days or so — it helps put the brakes on rust. The weather pattern we're in right now doesn't favor diseases. Warm, dry days aren't conducive to most foliar diseases.”
A lot of Delta wheat was planted late and there's still time for the weather to change — and thus disease pressure to increase, says Cartwright. Right now, he's unsure how bad this outbreak will be. But Cartwright expects it will be on the “mild to moderate” side. Helping contribute to this belief: there aren't nearly as many susceptible wheat varieties in fields as there were several years ago when stripe rust hit the Delta hard.
“And weather patterns right now don't favor stripe rust being able to develop to extremely bad levels. That said, though, growers with excellent wheat crops with high-yield potential — that are known to be susceptible to stripe rust — should be scouting intensely. If they find hot spots, given how early it is in the spring, they should strongly consider a fungicide treatment. Frankly, though, most of our fields aren't in that kind of shape.”
Some fungicide applications started going out in Mississippi towards the end of the first week in April, says Erick Larsen, Mississippi Extension wheat specialist. There's been more stripe rust show up since then.
“I've been hearing from consultants scouting wheat. Most of the stripe rust that's found has been around the Mississippi River levee. We're hoping the warm daytime temperatures will prohibit the outbreak of rust. The nighttime temperatures we're having are conducive to rust, but I hope they'll inch up some more.”
Larsen says the Mississippi wheat crop looks fair.
“A lot of the success of the wheat will depend on whether or not producers made timely fertilizer applications — particularly this spring to help the wheat tiller and get up to speed since it was thin going into winter,” he says. “If nitrogen applications went out too late this spring, the wheat won't be able to recover and realize full yield potential.”
To deal with stripe rust, Arkansas producers can choose between five fungicides currently registered for wheat. As stripe rust has shown up repeatedly over the last few years, Cartwright and fellow researchers have done a lot of testing of those on the disease.
“The old standby, Tilt — or products that contain Tilt, like Bayer's Stratego — are what many farmers go with to combat stripe rust. The other two products, including Quadris, are fine but they probably need to be on the crop before stripe rust gets a really good foothold. The Tilt materials have some kickback, even if infection of a crop has progressed some. Quadris is more of a preventative on wheat for this particular disease. All of them will work if you get the timing right, though.”