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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 that makes 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," Ohm says.
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.
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."
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.
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