Writer: Rod Santa Ana III, (210) 968-5581, r-santaana@tamu.edu
Contact: Dr. Tom Isakeit, (210) 968-5585, t-isakeit@tamu.edu
WESLACO — The discovery this week in deep South Texas of a devastating fungal disease could have serious implications for sorghum growers throughout the United States.
Known as ergot (pronounced ERR-got), the disease has an extraordinary capacity to spread. It reduces grain yields, damages the quality of seed, and threatens lucrative export markets.
The discovery was made in a field where sorghum had sprouted from last year’s crop in the Lower Rio Grande Valley of Texas by Dr. Tom Isakeit, a plant pathologist at the Texas A&M Agricultural Research and Extension Center at Weslaco.
“The heads appear to have been infected in late February or early March,” said Isakeit, “and there’s concern this disease will quickly spread throughout the United States this year.”
Ergot is also commercially important because quarantine restrictions are imposed against it by many countries, Isakeit said.
Because of warm climates at the time of flowering, ergot is not expected to severely affect grain sorghum production in South Texas. The disease could, however, continue its northward trek via forage sorghum in Central Texas, and eventually affect sorghum grown for seed in other parts of the state and nation.
Sorghum is a cereal grass with corn-like leaves and a thick stem. Its grain is produced in a cluster atop the plant and is used in livestock feed. It is grown for human consumption in some parts of the world.
First reported in India in 1917, sorghum ergot was restricted to Asia and Africa until 1995 when it caused serious losses in Brazil, covering 800,000 square kilometers (320,000 square miles) in a week. It then spread quickly throughout South and Central America.
As late as February, the disease was confirmed in Puerto Rico and Tamaulipas, Mexico.
“The finding of this disease in South Texas near Progresso, Texas, suggests that the ability of the airborne spores of this fungus to spread over great distances should not be underestimated,” said Isakeit.
Sorghum is the second most important feed grain in the United States, with an approximate farm value of more than $1 billion in Texas alone. In 1997, it’s projected that 12 million to 13 million acres will be planted in the United States. Texas grows between 2 million and 3 million acres of sorghum.
But Texas could be especially hard hit by the disease since it produces almost 90 percent of all sorghum seed grown in the world. The state’s sorghum seed production is concentrated mostly in the Panhandle and High Plains area of the state. Seed harvested from areas with ergot, said Isakeit, could be rejected by other countries.
Other key producing states, including Kansas, Nebraska, and South Dakota, could also be affected since those areas have cool and windy climate conditions that favor ergot.
Ergot is a fungal disease that infects the floral parts of the sorghum plant that would normally develop into seeds. It reduces both grain yield and quality because it replaces the seed with a fungus growth that produces a sticky fluid known as honeydew. The honeydew spills out over other seeds on the head, making harvest threshing difficult and encouraging the growth of saprophytic fungi that blacken the head.
As of now, there are no effective controls of ergot. Brazil and other countries have used expensive fungicides, but they have not been researched in the United States to determine proper dosages, nor have they been approved for use.
“The finding of ergot here in South Texas is an early warning signal that will provide a lead time to begin addressing the educational, research, and regulatory issues of this disease should it continue to spread northward,” said Isakeit.
A research and education response to the threat of ergot is already under way in this country and involves state and federal agriculture research agencies.
Texas A&M researchers throughout the state are working closely with U.S. Department of Agriculture-Agricultural Research Service researchers as well as with their Mexican counterparts in Rio Bravo, Tamaulipas, to determine effective treatments and to educate U.S. growers.
“We’ve begun tests here in South Texas to determine effective fungicide treatments which are applied both to the seed and flowering heads,” Isakeit said.
But these treatment add greatly to the cost of production and would be used only by those who produce sorghum for seed, he explained.
Texas A&M is also studying the epidemiology of ergot with countries that are dealing with the disease, training Extension agents and producers to recognize the disease, and conducting field tests of alternative chemicals and controls in all of Texas’ major sorghum-producing areas.
Pending federal and state funding, Texas A&M plans to also begin research to genetically engineer sorghum that is naturally resistant to ergot.
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