Preventive use of fungicides can limit corn disease damage

The bacterial disease is relatively common in northern Midwest areas such as Nebraska or Indiana, and many a southern farmer has mistakenly blamed Goss’s wilt disease for symptoms that were often caused by drought stress or other diseases.

Corn growers in a four-parish area of louisiana got a surprise education on plant pathology in 2013 that they may wish they could have skipped: a bacterial disease called Goss’s wilt disease.

Clayton Hollier, Louisiana State University AgCenter plant pathologist says growers in the northeast parishes of East Carroll, West Carroll, Madison and Tensas contended with the disease.

While it’s not a new disease, its discovery in the southern growing region is a first.

The bacterial disease is relatively common in northern Midwest areas such as Nebraska or Indiana, and many a southern farmer has mistakenly blamed Goss’s wilt disease for symptoms that were often caused by drought stress or other diseases.

But Louisiana actually documented the disease in the state’s corn crop — the first time it has ever been found in the South.

“It was certainly a surprise, because we weren’t expecting it,” says Hollier. “It was found and called to my attention, and then all of a sudden I was seeing symptoms in corn that I hadn’t seen before.”

He’d read about the disease in years past and had seen images of it, so he took samples of the suspected Goss’s infestation and sent them to the LSU AgCenter for further testing. A diagnostician confirmed that the pathogen involved was indeed Goss’s wilt.

Yield damage caused by the disease in the four-parish area appears to have been negligible, but in individual fields affected there were large circular patterns where symptoms were found.

Hollier is currently evaluating harvest map data to calculate how much yield was actually lost in those diseased circles.

The fields found to have Goss’s wilt disease were planted to three different corn hybrids produced by a single company. However, susceptibility to the disease is not uncommon among the corn hybrids planted in the Mid-South.

While plant pathologists compile and evaluate the harvest data to determine the severity of the 2013 disease outbreak, several unknowns remain.

  • How did Goss’s wilt disease find its way to the Deep South?
  • What is the overall damage potential from this bacterial disease?
  • Have enough crop residues been destroyed to prevent the disease from recurring in 2014?

“It is scary because it is new,” says Hollier. Using the control methods recommended by his counterparts in the Midwest, he suggests northeast Louisiana’s corn growers destroy crop residue and bury residues in the soil to allow the soil micronisms to further break down the plant material. It also is recommended that affected fields be rotated to a non-host crop, such as soybeans.

“Hopefully that’s something growers will keep in mind when they plant next year,” he says.

In addition to the battle with Goss’s wilt disease, Hollier says the state’s corn growers contended with a few “hot spots” of northern corn leaf blight disease. Southern corn leaf rust was also present in 2013, but it made a relatively late appearance in the region.

“There were a few spots that were advancing quickly enough and early enough that we recommended treatment, but that certainly was the exception to the rule. In most cases, the cost of fungicide applications would not have paid for themselves.”

In Mississippi, northern corn leaf blight, southern rust, and gray leaf spot were the three major corn diseases present in 2013.

According to Tom Allen, plant pathologist at the Delta Research and Extension Center at Stoneville, northern corn leaf blight was especially prevalent in fields planted to continuous corn without a defensive hybrid.

Justin George, an independent crop consultant at Merigold, Miss., says his main disease concern in 2013 was common rust. But, he says, the disease didn’t threaten his growers in sufficient numbers or result in sufficient damage.

“Northern corn leaf blight is another disease that deserves attention and gets our attention each year,” George says.

“In 2013, it progressed early in the season and then kind of played out. That’s unusual. The disease’s infestation timing was at tasseling in June, so on susceptible varieties we did use a fungicide as a preventive. It never fully developed as a disease issue.”

According to George, incidents of the disease, in both continuous corn and soybean-corn rotation fields, did seem to be variety-specific.

He contends that there is plenty of research data showing that yield enhancement is provided with a fungicide treatment, especially when disease pressure is present. As a result, he did recommend a fungicide spray to many of his growers.

See more articles from the Southern Corn and Soybean Production Guide!

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