Amarillo, Texas
March 31, 2009
The wheat curl mite is a minute
menace that wreaks havoc on the region’s wheat crop; but it has
no enemies currently that can take it out. That doesn’t mean
Texas AgriLife
Research scientists aren’t trying to find ways to curb its
appetite.
Three AgriLife Research scientists, working under Dr. Charlie
Rush in plant pathology and Dr. Jerry Michels in entomology, are
taking a close look at the damage caused by the wheat curl mite
to determine some best management practices for producers and
researchers.
They explained their current research at the recent Southwestern
Wheat Research and Education Consortium meeting held in
Amarillo, a gathering of scientists from Texas, Oklahoma and
Kansas working on wheat issues.
Jacob Price, AgriLife Research associate researcher-plant
pathology, participated in a virus survey in 2008 that
encompassed most of the central U.S.
In the survey, the most common wheat viruses found in the 75
million acres of wheat across the U.S. – 3.3 million acres in
Texas – were wheat streak mosaic virus, wheat mosaic virus
(formerly High Plains virus) and a fairly recently discovered
one, Triticum mosaic virus.
These viruses all have one common factor; they are all vectored
by the wheat curl mite. And the hot spot for all three viruses
was Texas, Price said. Because there are no chemicals labeled
for control of the wheat curl mite, researchers must find other
ways to combat it.
Price said one way will be to work with wheat breeders.
“Because we found Triticum at such a high prevalence, it would
be wise for the breeders to work closely with the pathologists
when these new diseases come in,” Price said. “We can work
together to develop genetic resistance for problems facing us
now and those that might affect us in the future.”
Dr. Fekede Workneh, an AgriLife Research scientist in plant
pathology, has been working to model the gradient of severity of
wheat streak mosaic and its impact on grain yields across the
field.
Volunteer wheat and grass vegetation are the green bridges that
allow wheat curl mites to exist through the summer until the new
wheat crop starts growing. The most damage appears to occur if
infestation takes place early in the fall; however research is
under way to determine the impact of time of infection, Workneh
said.
The distance of these bridges from the wheat field can determine
the severity of the virus damage, Workneh said.
“If it is a distant source, you will see sporadic and random
occurrences across the field, because the mites are carried in
the wind and their population gets diluted and dispersed,” he
said. “But the closer the source of mites, you will see more of
a gradient virus infection in the field, beginning at the edge.”
Workneh's advice is for growers to plant in mid-October or later
if they know they have a source that will harbor the mites, and
they want to break the green bridge between that source and the
wheat crop.
“This probably is not practical advice for some, because wheat
destined for grazing is planted early so that there would be
enough forage for the cattle in the fall and winter,” he said.
“However, getting rid of any volunteer wheat nearby would
definitely reduce the risk.”
Chanda Henne, an AgriLife Research research technician in the
entomology program, is trying to help growers recognize what
plants, other than wheat, might serve as hosts for the mites.
She has verified that the wheat curl mite can be found on many
grasses in the Texas Panhandle.
Henne tested six warm-season grass species, including Texoka
buffalograss, Blackwell switchgrass, Hachita blue grama, Spar
Old World Bluestem, Wrangler Bermuda grass and Haskell sideoats
grama to see which ones serve as reservoirs for the mites or
carry the virus.
Her study was conducted at the AgriLife Research station near
Etter, where these grasses are growing under full irrigation,
limited irrigation and dryland conditions.
While she has been collecting data for only about five months,
she’s found the switchgrass and blue grama grasses had
significantly more mites than the other species. Both of these
are native species and commonly used in the Conservation Reserve
Program fields.
“Every time we went out there to sample, the mites were present,
but they were not always present on all species,” Henne said.
“The only grass species that had mites on it every time we
sampled was blue grama.” |
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