Fungicides, cultural practices: Fight seedling diseases to protect cotton yields

Oh, what could have been. According to USDA, west Tennessee cotton producers made an average yield of 686 pounds of lint in 2002. While that's not bad for the region, yields might very well have been over 830 pounds per acre had growers not lost 20 percent of their yield potential to seedling disease in 2002.

“In fact, 2002 was the worst seedling disease season we have had in my 30 years,” said Melvin Newman, University of Tennessee plant pathologist. “We made a good crop on average, but it didn't turn out that way on everybody's farm.”

Any year with unfavorable planting conditions is a bad year, but last spring was especially so because a lot of farmers were trying to cut back on expenses and did not use fungicides, Newman said.

Newman cautions that there's no silver bullet for seedling disease control. When the weather turns adverse, there's nothing that's a sure bet. But it's better to stack the deck in your favor, because cotton is a very susceptible plant to seedling disease.

Cotton producers can fight seeding disease through a combination of chemical control and cultural practices, according to Newman.

Cultural practices include turning crop residue under as soon as possible. Also, crop rotation with soybeans or corn will help prevent the buildup of organisms pathogenic to cotton seedlings.

Planting on beds helps in some seasons by providing better drainage and warmer soil temperatures. Use certified seed or high quality seed with a germination of 80 percent or higher. Plant only when soil temperatures reach 65-70 degrees and are expected to remain that high or higher for an extended period of time.

Newman tested 15 soil fungicide options in 2002, including four in-furrow granular fungicides, two in-furrow plus insecticide combinations, seven in-furrow sprays and two hopper box treatments.

“Many of the in-furrow treatments we recommend within each category have equal potential for control,” he said. “Whether you use Ridomil Gold plus Terraclor or something else, they're all virtually the same thing. Just pick one you can get a good deal on.” (Note: Quadris and Ridomil Gold EC are available in a new in-furrow fungicide co-pack in 2003. The co-pack will be called Quadris Ridomil Gold fungicide.)

In addition, strobilurin materials such as Quadris are performing well under pressure in Newman's plots.

In 2002, Jackson, Tenn., producer Joe Couch went with Quadris in-furrow because “it's a lot more convenient to handle during planting, and we also used a seed treatment.”

“Seed treatments for combating seedling disease are getting better, although they don't provide the level of treatment of an in-furrow fungicide,” Newman said. “Strobilurins are also becoming a popular seed treatment. They're very strong on Rhizoctonia. And that's where we have most of our problems in west Tennessee.”

According to USDA, west Tennessee cotton acreage will be up in 2003. Couch, who farms 3,200 acres of cotton, 2,000 acres of soybeans and 1,500 acres of soybeans, says “It's always been the crop that's made us more money.

“We need to pay extra attention this coming year, with El Niño (potentially creating a wetter planting season), and high seed prices,” Newman said. “The fact is we just can't afford to replant. You're already in the losing column if you're replanting.

“I would rather err on the side of too much seedling disease control than not enough.”

According to Newman, a 12-year study at the University of Tennessee's Milan Experiment Station showed an average of $100 of clear profit per acre per year for the use of an in-furrow fungicide compared to an untreated check. Some years, there was very little savings, but some years there was a lot. It's not consistent, but the savings were $1,200 per acre over 12 years.

e-mail: [email protected].

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