Sugarcane diseases lead growers to new varieties

Johnny Morgan, Gravois, Kenneth, Hoy, Jeffrey W.  |  7/31/2009 6:54:49 PM

News Release Distributed on 07/31/09

As the sugarcane planting season begins to ramp up, most growers will be leaning toward newer varieties this year.

The challenge faced by sugarcane growers is sugarcane rust, a disease that was first found in Louisiana in 1979, said Dr. Kenneth Gravois, LSU AgCenter sugarcane plant breeder and coordinator of the AgCenter’s Sugar Research Station in St. Gabriel.

Gravois said the once-dominant LCP 85-384 sugarcane variety – commonly referred to simply as 384 – was resistant to rust until about six years ago.

“The 384 variety, released in 1993 by the LSU AgCenter, in cooperation with U.S. Department of Agriculture’s Agricultural Research Service Sugarcane Unit in Houma and the American Sugar Cane League, was a once-in-a-lifetime variety,” Gravois said.

“Yield potential increased by 25 percent, and stubbling or ratooning ability was the best we’ve ever seen,” he added, referring to the sugarcane plant’s ability to regrow and produce profitable crops in several consecutive years.

“Instead of making three or four crops, you could make four or five crops off of a single planting,” he said.

When it was released, 384 was resistant to all of Louisiana’s major sugarcane diseases, Gravois said.

“The one thing it was susceptible to was the sugarcane borer, but we have insecticides that can control that,” he said.

Gravois said the 384 gave farmers a major advantage because they had to plant only about 15 to 20 percent of their acreage each year. This equates to money in growers’ pockets because planting is one of the most expensive parts of the production process.

By 2004, 384 accounted for up to 91 percent of the state’s total sugarcane acreage.

“As 384 acreage increased, Mother Nature adapted, and so did the rust organism,” Gravois said. “That’s what happens when you have a single variety on a majority of your acres.”

New varieties show promise as replacements for 384, but none is totally resistant to rust, said Dr. Ben Legendre, LSU AgCenter sugarcane specialist.

One of the newer varieties growers are favoring is HoCP 96-540, which has become the most popular variety grown in south Louisiana, Legendre said.

“There are some fields across the southern part of the state in 540 that have a tremendous infection of rust, and now we’re worried that 540 maybe as susceptible as 384,” he said.

Rust has been the biggest problem for the sugarcane industry in recent times, said Dr. Jeff Hoy, an LSU AgCenter plant pathologist. The ability of this disease pathogen to overcome varietal resistance continues to cause major difficulty.

“All of the varieties released after LCP 85-384 were resistant to rust at the time of their release,” Hoy said. “However, three varieties – Ho 95-988, HoCP 96-540 and L 99-226 – have now become susceptible.”

The LSU AgCenter’s variety selection program will continue to develop rust-resistant varieties, Hoy said, but experts are formulating best management practices to minimize losses to rust on the farm.

Hoy said researchers are developing an alternative control program using fungicides, and he expects their use increase.

Johnny Morgan

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