Lubbock, Texas
September 21, 2005
If an ounce of prevention is worth
a pound of cure, what is a pound or a ton of prevention worth?
For High Plains cotton producers, the answer could be an entire
field or an entire crop when bacterial blight rears its ugly
head.
"Bacterial blight typically shows up on the High Plains in July
and August," said Dr. Terry Wheeler,
Texas Agricultural
Experiment Station plant pathologist based at Lubbock. "The
culprit is a bacteria that survives on plant debris littering
the soil. Wet field conditions – for example, two to three rain
showers in a month – triggers it.
"It spreads wildly, because the bacteria can be blown by the
wind from field to field. The first symptoms are dark-colored
leaf spots. It spreads across leaves, causing them to fall off.
If it reaches the boll, it can infect and damage the seed
inside. There are no seed or foliar treatments for it."
A major outbreak occurred on the High Plains in 1997. Damaging,
but local, outbreaks occurred in 1998 and 1999, Wheeler said.
High Plains cotton farms typically range from a few hundred to a
few thousand acres. An acre is roughly the size of a football
field, minus the end zones. Dryland yields in this region range
from one-half to one bale per acre, while irrigated acreage
normally produces one and one-half to two 480-pound bales per
acre.
An untreatable disease that takes out an acre of one-bale cotton
could rob a producer of more than $200, given a market value of
50 cents per pound. Even a little bacterial blight in the
region's 3.7 million cotton acres could have significant
economic impact.
Widespread concern from cotton seed companies and producers led
the Plains Cotton Growers, Inc., the state's leading cotton
producer association, to fund the blight screening project from
2000 onwards.
"We raise our own bacterial blight inoculum in the lab here at
the Lubbock research and extension center," Wheeler said.
It takes two days to raise enough blight inoculum in the lab to
spray 10 acres. Research technician Michael Petty spends about
one month spraying plots of cotton at several different
locations.
"We start at the cotton nursery maintained by Dr. John Gannaway,
Experiment Station cotton breeder at Lubbock," Wheeler said.
"Then we branch out to nursery acreage owned by different seed
companies.
"We mix the inoculum with a special sticking agent in a clean
50-gallon tank and apply it through large nozzles on a four-row
sprayer mounted behind a tractor. It's a slow-speed application
because we cover only about one acre with each 50-gallon tank
mix."
Two to three weeks after each spray application, the researchers
return to the field and rate the cotton plants for symptoms of
bacterial blight.
Because the screen affects only a few leaves on each plant, and
does not spread to other areas of the field, it has been very
well received by seed companies, Wheeler said.
"When we finish a screen, we come out of the field with a
resistance/tolerance rating for each variety," Wheeler said.
"Then we share that information with the seed companies and
producers. The screening project is a service component of our
plant pathology research.
Research was used to develop this procedure, but now our time is
spent executing the procedure for everyone's benefit.
"Bacterial blight is a 'sleeper' that we don't want to forget.
We know it's out there, but we don't know when or where it might
explode again.
Our goal is to get the seed companies the information they need
to breed and select for better blight resistance as they develop
new varieties. Prevention is our best protection."
Writer:
Tim W. McAlavy |