EPA Grants Emergency Exemption to TOPGUARD Fungicide

Texas cotton growers are on track to regain millions of dollars in lost yield potential now that the U.S Environmental Protection Agency (EPA) has granted a Section 18 emergency exemption to TOPGUARD, a proprietary fungicide produced by Cheminova, Inc., that targets the devastating fungus that causes cotton root rot disease.

Texas AgriLIFE Extension Service plant pathologist Tom Isakeit and Rick Mizenmayer–the Texas AgriLIFE Extension Service IPM specialist for Runnels, Tom Green and Concho Counties–evaluated TOPGUARD in field trials.

“In one of our TOPGUARD trials, we saw yield increases between 20 to 60 percent when cotton root rot was controlled,” relates Isakeit.  This is significant as cotton root rot is estimated to cause yield losses of as much as $40 million per year. Caused by the Phymatotrichopis omnivora fungus, cotton root rot is a chronic problem in some regions of Texas.

Bill Belew, who farms near Winters, TX, witnessed TOPGUARD’s performance in Texas AgriLIFE Extension Service field trials. “There was a black and white difference between plots treated with TOPGUARD and untreated check plots,” says Belew. “The reduction in cotton root rot was about 90% percent.”

Belew raises more than 1,000 acres of dryland cotton. He petitioned for TOPGUARD to receive the Section 18 exemption from EPA. “We need TOPGUARD to continue to grow cotton competitively in our area. With TOPGUARD, we can add yield potential to very productive farmland,” he says. 

Belew experienced the heavy toll cotton root rot exacts in a wet year. Five years ago, he relates, one field without cotton root rot yielded an average of 800 pounds per acre. In a field affected by the disease, average yields dropped by about 50%. Both fields received the same fertilizer treatments, were planted to the same variety on the same planting date, and received about the same amount of rainfall, emphasizes the grower. He attributes the yield reduction directly to losses caused by cotton root rot. 

 West central Texas grower John Wilde also cheers TOPGUARD’s approval. “We’re confident in TOPGUARD, because Dr. Isakeit evaluated it in a lot of test plots around the state,” says Wilde.  “In trials on our farm, TOPGUARD has proven to be an economical safeguard against cotton root rot.”

Wilde and his sons Douglas and Matthew farm 4,000 acres of cotton near San Angelo. “A lot of farmers in the Blacklands have stopped producing cotton and are planting dryland corn instead, due to an inability to control the cotton root rot fungus. They don’t have other crop options,” notes Wilde. He predicts that a lot of acres may return to growing more profitable cotton now that growers can use TOPGUARD.   

Also, with TOPGUARD applied, Wilde anticipates a better  harvest.  Cotton root rot reduces fiber quality. The disease rots the roots, plants die prematurely and debris from those plants get harvested with the cotton. That causes lower grades and reduced micronaire. Growers can lose two to four cents per pound of cotton, Wilde points out.

“It’s a big deal to get a Section 18,” declares Ken Pooley, who grows cotton along the San Marcos River in south central Texas. In a typical year, his area of the state receives about 30 inches of rain. While cotton root rot does not cause significant damage in dry years, he notes, it causes havoc in wetter years. In a bad year, growerscan lose 30% to 50% of their crop to cotton root rot.

The disease is very costly, explains Pooley, in part because cotton is a high value crop which requires significant investments—such as in fertilizer and seed—to grow. Any yield loss is significant.