Stripe rust hitting Arkansas wheat

“I got a little comfortable (the first week of April) thinking the stripe rust wouldn’t be as serious as was first suspected. But after seeing fields this week, I’m shocked at how quickly the disease has developed in just three days,” says Cartwright, Arkansas Extension plant pathologist.

“I was walking in fields yesterday and 50 feet in, my pants and shoes were orange from the fungus spores,” he noted. “The disease is active and all over the place. We’ve put out an alert that, at least for the next few days, it’s critical for growers – especially those below I-40 – to get out and check their wheat. East-central and southeast Arkansas wheat fields are getting a whole lot of fungicide treatments right now.”

Typically, stripe rust moves from south to north. If weather conditions (cool nights and warm days, which are great for stripe rust) continue, the disease will keep marching north, says Cartwright. Next week, farmers north of I-40 need to start checking their fields carefully, he says.

“Without a hot night or two to slow this down, we could be in even more trouble.”

April is the “disease season” for wheat. About this time in 2000, Arkansas experienced a big stripe rust epidemic.

“At that time, it became obvious to those of us that work in wheat that fungicides are very important,” said Cartwright. “By using them, we averted a major loss in about 300,000 acres of wheat.

“That epidemic, we felt, was somewhat unusual. Normally, stripe rust epidemics of that magnitude are rare – maybe one every 10 or 15 years. We documented some field losses of 50 percent in 2000. Fields that were treated cut 70 bushels per acre dry. Untreated fields were cutting in the low 30-bushel range.”

In such situations, growers are incredibly fortunate to have some effective, registered fungicides, says Cartwright. With this particular disease, fungicides are about the only option growers have.

On wheat, Arkansas has at least four fungicides registered for use through early heading. It’s important not only that these fungicides are available, but also that they’re registered so they can be used in the most effective manner, says Cartwright.

“Years ago, we had several fungicides that were registered in a way that we couldn’t use them after growth stage 8 (normally, far too early to spray). Now, fortunately, we have a much wider window for spraying.”

Arkansas already has a lot of damaged wheat from flooding and heavy rains. With prices what they are, damaged wheat fields probably won’t get the extra expense of a fungicide. But the highly productive wheat fields – those with 70 bushel-plus potential – will be scouted carefully and, if needed, a fungicide will be applied, says Cartwright.

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