Early
Detection and Treatment Critical in Reniform Nematode Control,
Expert Says
Auburn,
Sept. 10, 2002 --- More than a decade ago, a low-yielding cotton
field prompted one baffled west Alabama cotton producer to ask a
question.
Dr. Bill Gazaway, a
retired Alabama Cooperative Extension System plant pathologist,
continues to research nematodes and work with producers to reduce
their damaging effects. Their spread throughout Alabama should
surprise no one, he says, considering their ability to adapt to a
wide variety of soils.
"My family has been
growing cotton in this field for more than 100 years, so why am I
picking almost 400 pounds less cotton?" he asked, pointing out
that he had done as much as, if not more than, earlier generations
to maintain the field’s fertility.
The question was
directed to Dr. Bill Gazaway, an Alabama Extension plant
pathologist, who offered a simple, straightforward answer: reniform
nematodes, a problem earlier generations likely had never
encountered in all the years they farmed the field.
First detected in
Alabama more than four decades ago, reniform nematodes have spread
to all of the major cotton-producing areas in the state and are now
considered the state’s most destructive nematode. While most of
the problems associated with nematodes were originally confined to
south and central Alabama, serious outbreaks have occurred in the
Tennessee Valley of North Alabama since 1994.
"Their spread
throughout the state shouldn’t surprise anyone," Gazaway
says, "considering their ability to thrive in the soil, survive
under adverse conditions, and reproduce on a wide variety of crop
and weed hosts."
Nematodes can be spread
by flooding, contaminated cotton seeds and even animals, though
contamination most often occurs when farm equipment is carried from
infested fields into uncontaminated ones. That is why Gazaway and
other experts recommend washing or steaming equipment before it is
used in "clean" fields.
Gazaway retired from the
Alabama Extension System in 1999, but his retirement has provided no
harbor for the nematodes. He continues to conduct research on the
pest and to advise farmers on what they can do to contain their
damage.
Based on 20 years of
close observation of reniform nematodes, Gazaway stresses that early
detection and treatment are critical factors in controlling the
pest.
The first rule of thumb,
he says, is to never underestimate the nematode’s adaptability.
"The reason they
spread so easily is because of their unique ability to survive in
dry soils and dry weather conditions," Gazaway says. "They
can survive in a clod of completely dried dirt for six months. All
it takes is a little moisture for them to become active again."
"Very few other
types of nematodes survive under these conditions."
Second, but perhaps most
important of all, is getting a handle on the nematodes before they
damage cotton seedlings.
"Reniform nematodes
begin feeding on the roots of young cotton seedlings soon after the
seed germinates," Gazaway says. "It’s very important to
protect cotton seedlings from nematodes at the point of emergence,
say from six to eight weeks."
"That’s the
critical time. Control measures used later in the crop seasons to
combat heavy infestations are also important, but you really want to
suppress populations long enough get the plants with established
root systems off and growing."
Gazaway often describes
reniform nematodes as a stress pathogen – and for good reason.
"Reniform nematodes
devitalize the root system’s ability to take up water and
nutrients," he says. "Cotton plants can do pretty well so
long as moisture and other growing conditions are adequate. But as
soon as adverse weather conditions set in, that’s when these
nematodes really add the kick."
This, Gazaway says, is
another reason why it is vital for producers to sample their fields
for signs of the nematodes and, if the sample turns up positive, to
treat for nematodes early in the season to reduce pests’ changes
of getting a sufficient toehold on the plants’ root systems.
(Source: Dr.
William Gazaway, Retired Extension Plant Pathologist,
334-844-5505)
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