sealPurdue News

July 2001

Sprinkler system promotes growth of wheat fungus

WEST LAFAYETTE, Ind. – This spring, a small portion of the Purdue University Agronomy Research Center may look more like an artist’s expression than a scientist’s research tool.

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A thousand white, plastic pipes, each four feet tall, emerged from the prairie at eight-foot intervals. A nozzle on each showers a thousand times as many wheat plants with a cool, fine mist of water.

But this wasn’t art. It is the work Purdue agronomist Herb Ohm, graduate assistant Jim Uphaus and technician Dan McFatridge.

The trio assembled the one-of-a-kind fungus irrigation system for the first time last year. This year, Ohm doubled the coverage size, using 11,000 feet of pipe to cover a 1.5-acre wheat nursery.

The objective of the misting system was not to nourish the plant, but to promote growth of a fungus that could kill the very wheat it wets.

Fusarium head blight is the number one concern of wheat farmers," says Ohm, "particularly in the Midwest."

The December 1997 issue of the scientific journal Plant Disease reported the last major outbreak occurred in 1996, causing about $38 million in losses to farmers in Indiana and Illinois.

A 1993 epidemic in the northern plains (Minnesota, the Dakotas and Manitoba) caused losses estimated at $1 billion. The fungus creates a toxin which attacks only wheat, making the grain unfit for feed or food, causing illness in animals or humans who ingest it. In addition, any grain exposed to the disease will not germinate, damaging the seed crop as well.

Fusarium has been around for more than a century. But the increasing popularity of no-till and reduced-tillage farming in the past 15 years has caused the problem to mushroom. The fungus grows on the rotting corn or wheat residue left in the field from the previous year.

"Wet weather causes the fungus to develop and produce masses of spores that enter the wheat plant during the flowering stage," says Ohm.

Dry spring conditions inhibit the spread of the fusarium spores, making it difficult for scientists like Ohm to study the disease and produce genetically modified strains of wheat that are resistant to fusarium.

"Fusarium cannot be effectively stopped with fungicides," Ohm says. "In the future, I think controlling fusarium will require a combination of host resistance and some fungicidal application."

That’s where the misting system comes in.

The eight horsepower generator that powers the sprayers is turned on twice a day, early in the morning and late in the afternoon for 2-3 hours. Each nozzle puts about a gallon of water per hour on the ground. It’s enough to keep the ground moist but not muddy.

"We still need to get into the field to collect data," Ohm says. "Other irrigation systems would put out too much water."

Wheat is not a major crop in Indiana, and the plants infected with the virus on the agronomy farm pose no threat of spreading to surrounding farms, Uphaus says.

While the system is designed to promote the growth of the fusarium fungus, it also promotes growth of other important fungal diseases of wheat, including glume blotch, leaf blotch and powdery mildew. In a dry season like 2001, fungal diseases do not develop appreciably, making it difficult to distinguish susceptible and resistant wheat plants in the breeding nursery.

The fusarium research is expected to continue for another five to seven years, but Uphaus says preliminary results have already identified several strains that are resistant to fusarium.

Ohm has noted another benefit.

"The wheat in the misted area is several inches taller than in the nonmisted area of the nursery," says Ohm, who expects a yield rate of 100 bushes per acre, compared with a 60-bushel rate in the nonmisted wheat.

There are thousands of different genotypes represented in the nursery plot at the agronomy farm, but that is only a portion of Ohm’s fusarium research. Test plots also are being grown throughout Indiana’s varied soil and climate types. Ohm monitors other test plots near Evansville, Woodburn (east of Ft. Wayne), Wabash, Romney, Vincennes and at the Pinney-Purdue Ag Center near Valparaiso.

Source: Herb Ohm, (317) 494-8072;

Writer: Tom Campbell (765) 494-8084;

Purdue Ag Communications: (765) 494-2722; Beth Forbes, Ag News Coordinator,;

Purdue News Service: (765) 494-2096;

Herb Ohm displays the misting system now in place at Purdue University's Agronomy Farm. It took two months and more than 11,000 feet of 1-inch plastic tubing to assemble the system, which was designed to grow the wheat fungus fusarium head blight. Researchers hope to find ways to battle fusarium, as well as other fungal diseases of wheat, through the project. (Purdue Ag Communications Photo by Tom Campbell)

A publication-quality photograph is available at the News Service Web site and at the ftp site. Photo ID: Ohm.fusarium

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