July 21, 2008

Gray leaf spot threatens Kansas corn

The presence of gray leaf spot has exploded across east Kansas cornfields, raising concerns about yield loss potential, a Kansas State University plant pathologist said Friday (July 18).

The outbreak of the disease has occurred in the past 10 days across eastern portions of the state, said Doug Jardine, plant pathology state leader with the K-State Research and Extension. This raises the specter of yield losses, increasing the importance of field scouting, he said.

This is especially true in corn-following-corn fields or in situations where farmers are employing no-till. Jardine, who scouted numerous cornfields in the western half of the Kansas River Valley in the first week of July, said in nearly every field gray leaf spot lesions could be found within one to three leaves of the ear leaf.

The only exception to the rule appears to be southeast Kansas, which Jardine scouted on July 17-18. Most of the corn in southeast Kansas is mature enough that gray leaf spot is not likely to be a problem for the remainder of the season, he said. However, there is always the risk that humid weather and scattered thunderstorms will materialize in the region, bolstering the disease's prevalence.

Gray leaf spot, which is caused by a fungus, leads to a loss in sugar production, ultimately lowering yield potential.

According to the US Department of Agriculture, Kansas farmers planted 4.1 million acres of corn, roughly 5 percent of the entire US corn acreage.

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