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Researchers look for new Icon

Brooks Davis used to think his rice was sick from high pH soil, or perhaps salt or maybe herbicide carryover.

“We thought we had everything in the world,” he recalls. “But then, when we starting treating our rice with Icon, we found that 75 percent of our problems were related to lespedeza worms, which were trimming roots off the plants.”

Davis farms about a thousand acres of rice near Stuttgart, Ark. For Davis and other farmers with water weevil or lespedeza worm problems, Icon was the answer to their prayers.

Then, the manufacturer pulled the herbicide off the market for use in rice in 2004, and Arkansas rice farmers were left high and dry. They have had to resort to other tactics such as overseeding — and the increased risk of encouraging sheath blight — flooding earlier than usual, and using an insecticide which is less effective than Icon.

However, researchers at the University of Arkansas Division of Agriculture are searching for a replacement that will put a lid on the water weevils, lespedeza worms and chinch bugs plaguing the state’s rice fields.

John Bernhardt, a division researcher at the UA Rice Research and Extension Center at Stuttgart, estimates that Arkansas farmers treated about 400,000 acres of rice for lespedeza worm in 2005.

He says his efforts to find a replacement have been frustrated by the nature of lespedeza worms. “We’ll put out a test plot, and the insects will show up on the other side of the field from our test. We need a reliable site to work with.”

That may happen next year. Bernhardt says the EPA has cleared him to go onto a farm and use unregistered products under certain guidelines. “We may be able to do larger plots on farms that we know are infested with worms, and that will aid us in finding a replacement.

“We’ve been trying chemicals ever since we knew the maker was going to withdraw Icon from the market. We found one that would be a good replacement, but the company is not interested in registering it for rice. We thought they would jump at the chance to get half a million acres of rice.”

He says there are a number of other seed treatments and foliar applications he wants to test once he gets reliable test sites. He expects next year to be able to test several chemicals and find out which ones work.

“Then, we’ll have to see if the company or companies are willing to register it in rice,” Bernhardt says.

Gary Sebree has the same problem as Davis, his neighbor.

“I would say on the Grand Prairie, at least 80 to 90 percent of the true prairie ground has the potential for lespedeza worm problems,” he says. “They don’t seem as prevalent in heavier ground.

“When Icon came along,” he says, “it did such a great job that we tended to forget about it because it worked so well. We need an alternative because lespedeza worms are a major concern on the prairie.”

A replacement can’t come too soon for Chuck Wilson, rice specialist for the UA Cooperative Extension Service.

“Rice water weevils and chinch bugs were as bad last year as I can remember. They would have been controlled by Icon,” says Wilson. “We have some products for adult water weevils, but it’s the larvae that do the damage.

“Mustang Max is labeled for lespedeza worms. It’s a pyrethroid for surface application by flushing it in. In some places, it works well, but sometimes it doesn’t work at all. It has potential, but it’s not the cure-all farmers are looking for.”

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