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EPA allows farmers a weapon against cotton root rot

EPA allows farmers a weapon against cotton root rot
Topguard was a fungicide few would have predicted to play a role in cotton root rot control. Topguard is an older chemical, used in other parts of the world since the 1980s. It was more recently brought into the United States to deal with soybean rust. The EPA has granted Texas a Section 18 emergency exemption to use Topguard to control cotton root rot.

When the news came down last week that the EPA had granted Texas a Section 18 emergency exemption to use Topguard to control cotton root rot, no one was happier than San Angelo farmer John Wilde.

“It’s a dream come true,” Wilde said. “This exemption means we can compete economically with good quality cotton. We’ll make better yields and better quality.”

Wilde, who farms with his two sons, Doug and Matt, says raising cotton without root rot infestations could mean from 2 cents to 4 cents a pound more for their cotton, just on improved quality. “We’ll have less low mic cotton, better grades and better staple,” he says.

They’ll also have less “barky” cotton. “Cotton picks up bark from the dead stalks caused by root rot,” he says. “Mills can remove leaf from cotton but they can’t remove bark.” He says cotton from root rot-infested fields typically gets discounted from 2 cents to 4 cents a pound.

Yields also will improve since root rot can cut production by 50 percent or more.

Wilde and his sons have had a vested interest in finding a root rot control. They’ve provided a “root rot nursery” to Texas AgriLife Extension specialists Tom Isakeit, plant pathologist, and Rick Minzenmayer, integrated pest management, for six or seven years. The 8- to 10-acre plot has a history of cotton root rot and provided Isakeit and Minzenmayer an opportunity to screen fungicides and applications methods in a location with consistent infection levels.

“It was worth the cost to Doug and me,” Wilde says. Doug typically farms that field, and he lost money by keeping it in continuous cotton and setting part of it aside as a check plot. “That field has a lot of root rot,” John says.

Isakeit has a lot of time and energy invested in the project as well. “I started screening materials as a stem drench in 1999,” he says. He says little work had been done on cotton root rot since the 1980s after research projects ended at Texas A&M and in Arizona. “Our efforts really took off with Texas state support,” he says.

They started screening products on Wilde’s farm by applying them through subsurface irrigation tape. “For the first three years we found no positive results,” Isakeit says. “In 2008, we tried Topguard and were pleased to see it worked, but at very high rates.”

The real breakthrough, he says, came in 2010. “We applied the material at planting and at 1 pint to 2 pints per acre, and we had good response. We repeated that in 2011.”

Results last year, though disappointing at many locations because of severe drought—and no root rot infection—showed good response at locations away from San Angelo and gave them enough data to submit a request for the Section 18 exemption.

They also refined the application method last year. Instead of applying in the furrow at planting, which some research indicated could result in phytotoxicity, they applied Topguard through a T-band, which dispersed the material along the furrow wall. It’s that application method that’s labeled by EPA.

The label also calls for 1 pint to 2 pints per acre and no more than one application per year.

Minzenmayer says the product and application method “looks promising. We’ve learned a lot, but there’s still a lot to learn.”

Research continues

“We’re not finished,” Isakeit says. “Last year, because of the drought, was not a good year to test root rot control. We had a lot of experiments set up but with drought, we had no disease in many locations.”

He says ongoing research will look at ways to increase efficiency and save money. “It’s possible that we can reduce the amount of chemical applied,” he says. “It’s labeled at 1 to 2 pints per acre but we’ve seen best efficacy at the higher end of the range.”

He hopes continuing trials will show better application methods that will allow farmers to reduce application rates without sacrificing control.

The T-band application method has been adopted to prevent phytotoxicity. “We haven’t seen that in our trials,” Isakeit says, “but Cheminova (the manufacturer) found phytotoxicity in trials where they applied in-furrow and then had a rain soon after planting.” That application method will be one area of study. Currently, application with a T-band is the only labeled method.

He recommends that farmers follow the label exactly. “We don’t want them doing their own trials. They should get with their county Extension agents and let them help set up something,” he says.

Isakeit also plans to install sensors in some fields to monitor moisture and temperature to determine the correlation between those factors and incidence of the root rot fungus.

The recent exemption approval was “timely, even for the Valley, where they are just beginning to plant,” Isakeit says.

He and Minzenmayer urge farmers not to depend solely on Topguard to control root rot. “We were limited before. Rotation was about the only option farmers had to deal with root rot. And cotton was usually the best crop for irrigated acreage. But rotation will still help,” Minzenmayer says. “Cotton on cotton is not the best option.”

“We still need to follow a good IPM program,” Isakeit adds. “Crop rotation should be part of the overall cotton management strategy. Topguard is not a reason to go to a monoculture. Farmers still have to consider other pests, such as nematodes.”

Minzenmayer says root rot is a particularly damaging disease because symptoms come on late. “It doesn’t show until the bloom period and by then farmers have almost all their inputs out. In some cases, losses can be 50 percent to 60 percent.”

Harvest can be a big challenge, too, with dead stalks clogging machinery as well as reducing quality.

Isakeit says root rot does not occur in the Texas High Plains and has been only a minor problem in East Texas, where little cotton is grown any more.

“But we see pockets all over the rest of the state,” he says. “Thousands and thousands of acres are infected with root rot. Some growers have only a little; others have a lot.”

More Flexibility

With a new tool available, he says farmers across the Blacklands may be able to add cotton to what has become a corn monoculture.

Minzenmayer says farmers in the Rolling Plains may be able to plant cotton more often on the best irrigated land. “Most do not have enough water to grow corn with only 12 inches to 14 inches of irrigation. But, under normal conditions, they can make a good cotton crop with that much irrigation. Still, rotation will help.”

Isakeit says Topguard wasn’t a fungicide he would have predicted to play a role in cotton root rot control. “I was hoping to find control in one of the newer chemicals,” he says. “Those would be easier to label. Topguard is an older chemical, used in other parts of the world since the 1980s. It was more recently brought into the United States to deal with soybean rust. It’s surprising, but if they hadn’t brought it in for soybeans, we wouldn’t have tested it on cotton.”

Minzenmayer says Extension will offer grower meetings to explain how to use Topguard. “Application is very specific,” he says. “Label calls for 16 ounces to 32 ounces applied in a 5- inch T-band.”

“This is a great breakthrough in controlling cotton root rot, which affects so many acres in the Southern Rolling Plains,” says Randall Conner, executive director, Southern Rolling Plains Cotton Growers Association, Inc. “We are very pleased to have Topguard approved for use this year.”

So is Wilde. He figures some 2,300 acres of his cotton land is affected by cotton root rot. “I’m excited. Doug, Matt, Rick and Tom are also excited,” he says. “They’ve done worlds of work to get this product labeled.”

The process took some unusual twists and turns, he says, to get to this point. “We started with drip tape, and the strong dose they used at first gave us the discovery. Now, we’re down to the label rate and this application method is better.”

He said Texas AgriLife technicians Pam Halfman and Corey Clark also worked hard to get the testing done and the data collected.

It’s been a long time coming, Wilde says. “But we are thankful.”

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