Amarillo, Texas
June 7, 2006Wheat
producers have more than the drought cutting into their yields
this year, said two Texas
Agricultural Experiment Station researchers.
Dr. Tom Allen, Experiment
Station assistant research scientist and plant disease
diagnostician, saw more than 150 wheat samples sent to the Great
Plains Diagnostic Network lab this growing season, in addition
to 400-plus samples the plant pathology staff gathered across
the Panhandle.
Ninety-five percent of these
samples were diagnosed with the wheat streak mosaic virus. In
addition, 50 percent of the samples contained maize red stripe
virus, more commonly known as High Plains virus. Both diseases
are vectored by the wheat curl mite, Allen said. And so far,
there's no treatment for either the viruses or the mite.
The Great Plains Diagnostic
Network is a part of a national plant disease monitoring system,
which is divided into five regions. The Amarillo facility, a
satellite lab to one at Kansas State University, is operated
under the Experiment Station's plant pathology program, headed
by Dr. Charlie Rush.
Samples came by mail, through
Texas Cooperative Extension agents or were dropped off by
producers, Allen said.
They came from as far north as
Nebraska and as far south as Dallas and the Hill Country, Rush
said, making this one of the most widespread years for wheat
streak mosaic damage.
"Without question, wheat streak
mosaic virus is the No. 1 pathogen of wheat year in and year
out," he said.
An early indication this wheat
crop would have more problems than normal was the arrival of
samples in the middle of October, Allen said, "which is pretty
rare to see virus that early. "We've had quadruple the number of
samples as any previous year," he said.
Once a crop is diagnosed with
one of the viruses, there is little the producer can do, Allen
said. Widespread cases can reduce yields enough that only
grazing or making silage from the crop can salvage any income.
In many cases, the crop is "zeroed out" by insurance companies
and plowed up.
This year's virus started early
because of last year's crop, he said.
A hail storm across much of the
region shortly before harvest knocked the grain from the heads,
Allen said. These seeds germinated into a heavy volunteer wheat
crop, which went uncontrolled through the summer.
The wheat curl mite
over-summered on this "green bridge" and moved into the new
crop.
Control of volunteer wheat this
summer will be key to controlling the wheat curl mite that
vectors the disease, Allen said.
Rush and Allen believe the
Conservation Reserve Program grasses throughout the region also
might harbor the wheat curl mite.
"We don't have a good
understanding of the wheat curl mite and its ecology," Rush
said. "It holds on some grasses, but there's lots of work to be
done to understand what happens with these mites during the
summer."
Right now, he said, the only
other advice they can give to producers is to plant as late as
possible to reduce chances of severe wheat streak problems
again.
"We're trying to develop some
cultivars that can be resistant to wheat streak mosaic and could
be planted early and then grazed out," Rush said. "They would be
popular in this region and serve an important purpose."
The problem now, he said, is
any resistance breaks down in high temperatures. And not enough
is known about the wheat curl mite to tell producers when or
what to spray.
"There are big gaps in our
knowledge," Rush said. "But we are making progress and have
things working in the field that should provide answers in the
next couple of years." |