What is in this article?:
- 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.”