COLLEGE STATION — A new and potentially devastating grain sorghum disease in the United States has both long- and short-term ramifications equally critical to the industry.
At issue is how to protect this year’s crop from the spread of sorghum ergot (ERR-got), which swept across the entire South American continent in less than two years, while finding ways to prevent future outbreaks.
The discovery of ergot in a Texas field where sorghum had sprouted from last year’s crop in the Lower Rio Grande Valley was announced late last week. Ergot causes the flowers of sorghum heads to secrete a sweet, sticky fluid rather than grain causing significant losses in yield and quality.
“Ultimately, we probably will have ergot throughout the entire sorghum growing area of the United States,” said Dr. Richard Frederiksen, Texas Agricultural Experiment Station plant pathologist. “We had long argued that the one thing we (sorghum industry) did not want in the Western Hemisphere is ergot. So now it shows up. We have it.”
Texas producers have begun planting sorghum at the southernmost reaches of the state, and planting will proceed northward on up to 3 million acres through early summer.
To confront the problem, at least three efforts are racing through the decision-making process:
* Dr. Gary Odvody, Experiment Station plant pathologist at Corpus Christi, is assisting with paperwork that will ask the Texas Department of Agriculture to allow for an emergency authorization to use the fungicide propiconazole. It is available in the United States but not currently labeled for use on grain sorghum for control of ergot.
* Experiment Station scientists are joining with researchers in New Mexico, Kansas and Nebraska to propose collaborative research funding efforts to state and federal agencies.
* Farmers, through the Texas Grain Sorghum Producers Association headquartered in Abernathy, are fronting some $20,000 to initiate an education program to provide information on how to deal with the problem this year, according to Travis Taylor, TGSPA executive director.
“The allocation of $20,000 is the first step in the stairs to controlling this disease until we find out more about it,” Taylor said.
Indeed, little is known. Ergot was an Eastern Hemisphere disease until 1995 when it was discovered in Brazil having found its way there possibly on the shoes of travelers or shipments of planting seed. From Brazil, the disease spread quickly throughout South America, up through Central America and into Texas — all within two years.
One drop of the honeydew contains several million spores which can go with a whiff of the wind, or land on clothing or animals to contaminate crops when conditions are right. The fungus only affects unfertilized female flowers. Typically several hundred such flowers will develop on a sorghum head over a period of up to seven days, meaning that over a large field, the crop can play host to the spread of ergot for extended periods. Ergot likes to spread in cool temperatures which also happens to be the time that female flowers are less likely to be fertilized.
What is not understood, Frederiksen said, is the structural survival of the fungus. How does it know, for example, only to fire its pathogen at female sorghum flowers at the precise time they are susceptible to infection — prior to fertilization?
Frederiksen said researchers will attempt to find ways to interrupt the ergot life cycle using cultural and chemical methods and, more pressing to the current crop, will look at the most efficient rates and application methods to apply chemicals to kill the fungus in fields.
The Experiment Station researchers will conduct field trials in Mexico, where the disease is more prevalent, and in Texas laboratories where the fungus will be grown in conditions replicating those of Texas producing areas. Scientists also will try to determine other plants that may be hosting the fungus prior to its attach on sorghum.
“The economic threshold for a plant disease is different than that for insects,” Frederiksen said. “With insects you can do counts and make predictions about population buildup. With diseases, if you see it, it’s already too late.”
Frederiksen said farmers who typically grow sorghum as a grain crop are least likely to be affected, but those who produce the crop for planting seed should be most concerned. The High Plains area around Lubbock produces about 90 percent of the sorghum seed planted in the United States and much of the world, he said.
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