While Asian soybean rust seems to always be on a grower's mind, another rust, the southern-corn type, is appearing too often for many southern producers. But Wayne Dulaney believes his corn fungicide program, aimed first at boosting yields, is preventing rust damage on his Mississippi farm.

Dulaney's family farms at Clarksdale, MS. They also run a seed business. To help prevent southern rust and other diseases, they apply fungicides on virtually all corn acres, whether there are disease symptoms or not.

“We've had this program for three years and have conducted some extensive testing,” says Dulaney, whose 2007 crop averaged 206 bu./acre. “We've had very little disease pressure, even during wet periods. We've seen our corn yields easily increase by up to 15 bu./acre and the crop has been free of disease problems.”

In 2007, southern rust roamed around parts of Mississippi, Arkansas and Louisiana, states that saw their corn plantings increase to 2.3 million acres, up from a total of 800,000 in 2006. It was yet another case of increased corn production thanks toa $3.50-4-bu. price on the table.

“Overall we were dry for most of the 2007 corn season, but good rainfall fell in early July over a 10-day period, making conditions right for southern rust development,” says Jason Kelley, Arkansas Extension feed grains agronomist. “If we would have had a few more days of rainy weather, we could have been looking at a situation similar to 2004.”

That year, Arkansas producers found at harvest that a lot of cornfields with southern rust had shut down prematurely. Yields were down 50 bu. or more. “The kernels weren't completely formed; not to the black layer yet,” says Kelley.“But the plants had to fill the kernel some way and it robbed the stalk. That led to a lot of weak stalksthat went down.

“We ended up with corn that should've made 200 bu. and ended up at 130-150 bu. A lot of that was because we couldn't pick the corn up off the ground,” he says.

Lodging results because southern rust defoliates the plant, which then turns to the stalk for resources to fill ears, says Scott Monfort, Arkansas Extension plant pathologist.

He recommends treatment witha propiconazole fungicide, suchas Tilt. “Headline, Quilt, Quadris (strobilurin fungicides) can be applied early for more of a protective role,” says Monfort.

Dulaney counts on the strobilurins to counter rust and other diseases. “We either put down 6 oz.of Headline or 14 oz. of Quilt,” he says. Cost of the applications is$12-15/acre.

“We like Quilt because it provides two modes of action. It's a strobilurin with a triazole. It givesa broader spectrum of control,” Dulaney says. “We're able to control anthracnose, leaf blight and other diseases, along with southern rusts.”

Dulaney points out that with the help of late-summer dry weather, some of his southern-rust-infested corn still managed to yield over 220 bu. “The late-maturing corn had help from the late-season weather,” he says. “But overall, our fungicide treatments are what help us offset southern rust and other diseases.” n Wayne Dulaney, Clarksdale, MS, has gained 15 bu./acre the past three years by routinely spraying fungicides to prevent southern corn rust and other diseases.