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Glyphosate drift in rice major problem in Arkansas

Glyphosate drift remains a huge problem for Arkansas rice.

“Drift has certainly gotten the attention of the state Plant Board (which is responsible for investigating drift complaints),” said Bob Scott, Arkansas Extension weed specialist at the recent Southeast Branch Station field day in Rohwer, Ark. “This year, approximately 47 percent of the complaints received by them regard glyphosate drift on rice. And it isn’t over — the late-season drift cases are still occurring.”

Until 2,4-D damaged thousands of northeast cotton acres, glyphosate drift was dominating phone calls at the Plant Board. Now, there are many calls on each problem.

“I was in a rice field yesterday with about 5 to 10 percent of the heads affected,” said Scott as he passed around blanked rice he’d pulled from a drift field. “This is officially known as ‘sudden glyphosate syndrome.’ The reason it’s sudden is the farmer may not realize his field has been drifted on until the heads emerge. At that point, suddenly he has a problem.”

The drift injury only occurs when the drift occurs after panicle initiation and can cause devastating yield drops. Uptake of the herbicide “is translocated into the point where the seed head is being developed. It interferes with seed development and reduces flag leaf. As far as symptomology, that’s what separates it from straighthead.”

Confusing the situation, Newpath drift can show similar effects.

“One difference between them is you’ll often see the Newpath drift immediately through leaf burn, a stunting of the plant, smaller seed heads, malformed seed heads and other things.”

It’s a common misconception that the drift is mostly caused by air applications. Approximately half of the drift complaints Scott works — “and that lines up with what the Plant Board has found” — are from ground applications. The difference is an aerial complaint may involve three fields while a ground complaint is only in one field.

“Most all the drift problems I’ve seen are associated with sprayings in excessive wind after panicle initiation. It only takes about 1 to 2 ounces of Roundup WeatherMax to blank seed heads in a rice field. At a 22-ounce per acre rate, all you need is a tiny fraction to drift.”

Has Scott looked at nozzles those responsible for the drift have been using?

“No, I haven’t. Most of the guys use air-induction, low-drift nozzles. But some don’t. There doesn’t seem to be a nozzle component to the problem.”

Can the symptomology be caused by other herbicides?

“As far as seed heads, the problem is often mistaken for straighthead. The reduction in the flag leaf is very characteristic of glyphosate damage. Something else to look at is any hemp sesbania or joint vetch in the field. If those are yellowed, it was probably caused by glyphosate. Newpath doesn’t hurt those.”

Editor’s note: to see this story unabridged, see the Delta Farm Press tabloid.


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