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Aug. 6, 2018
Site-specific technology aids nematode control when cotton fields turn to soybeans
By Fred MillerU of A System Division of Agriculture
Download MS Word version
Download PHOTO from Flickr: https://flic.kr/p/26TqT69
Related VIDEO: https://youtu.be/F3gTMUnBlwQ
FAYETTEVILLE, Ark. — Thousands of acres of soybeans in eastern Arkansas are under
attack from a tiny pest against which they have little or no natural defenses, said
John Rupe, professor of plant pathology for the University of Arkansas System Division
Root knot nematodes are plant parasitic round worms that are so small they are measured
in micrometers. They attack the plants at the roots where they cause swellings called
Those galls bind up a lot of the plant’s energy, in the form of sugars, that otherwise
would be used for plant growth and development. They also disrupt the movement of
water and nutrients through the roots. The result for soybean producers, Rupe said,
is a dramatic loss of crop yield.
Rupe said root knot nematodes can thrive on hundreds of plant hosts and are common
in sandy soils once used primarily for cotton production. Changes in crop prices in
recent years have led to a lot of cotton acres being converted to other crops, he
said and a lot of those acres are now planted with soybeans.
“Cotton is a good host for root knot nematode,” Rupe said, “and they like coarse,
loose soils like the sandy soils in many areas of east Arkansas and neighboring areas
of Mississippi and Louisiana.”
Rapid Research Response
To attack the problem of potential economic loss, Rupe obtained a USDA Critical Agricultural
Research and Extension grant. Also known as CARE, the grants are designed to fund
research in areas of immediate need when existing research leading to a solution is
As principle investigator, Rupe coordinated a research effort of scientists from the
U of A Division of Agriculture, Mississippi State University and Louisiana State University.
The researchers’ areas of expertise included plant pathology and nematology, soil
science and agricultural economics.
The research drew on existing research data and employed the latest technology and
time-tested scientific methodology to test nematode control strategies on cooperating
farms in all three states, Rupe said. They used replicated test strips in soybean
fields, including control strips in which no control strategy was used.
“There are no high-yield soybean varieties with good resistance to root knot nematode,”
Rupe said. “So we focused on nematicide soil applications and seed treatments.”
Crop rotation was not tested, Rupe said, because root knot nematodes thrive in such
a wide range of plant hosts that there are few options among rotation crops that would
help reduce the pest populations.
“Peanuts make a good rotation crop to control these nematodes,” Rupe said, “but peanuts
are not a practical option for most farmers.”
The research has shown that the most effective control strategy for root knot nematodes
is a nematicide chemical called Telone II. It’s a preplant fumigant that must be injected
into the soil about two weeks before planting, Rupe said.
“Telone II provides effective control,” he said, “but it’s expensive.”
Division of Agriculture economist Robert Stark, based at the Southeast Research and
Extension Center at Monticello, is working out the economics of cost versus return,
Rupe said, and those numbers will figure into recommendations the division is developing
for soybean growers.
In the meantime, Arkansas’ highly variable soil structures, especially in the Delta,
offer cost-cutting potential, Rupe said.
Land within a single field can vary from sandy soils to more densly packed silt loams
and clays, where nematode populations are lower or even nonexistent, Rupe said.
“We wanted to know if spot applications based on soil texture would offer sufficient
control of root knot nematode,” Rupe said.
Soil structure in test fields was analyzed and mapped using electrical conductivity
sensors from Veris Technologies, Rupe said. Finer, more compacted soils conduct electricity
more efficiently than coarser, looser sandy soils. The soil texture maps generated
by this system identify sandy areas in a field where root knot nematodes occur in
Results of the test applications were evaluated by digital image analysis from drones,
satellites and yield monitors on combines during harvest.
Tests in which Telone II was applied only in the sandy areas indicated that soil texture-guided
spot applications provided good protection against root knot nematodes.
Seed treatments offer good protection in areas where root knot nematode populations
are light, Rupe said. The protection is limited because seed treatments offer protection
for relatively short periods after planting.
Rupe said the research results are being disseminated through scientific and producers
meetings and presentations at agricultural research field days. Once useful recommendations
have been developed, they will be disseminated through county extension agents in
the partner states.
In the meantime, an animated video has been produced to explain and illustrate the
research. It will be shown at meetings and is available online: https://youtu.be/F3gTMUnBlwQ
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen
agriculture, communities, and families by connecting trusted research to the adoption
of best practices. Through the Agricultural Experiment Station and the Cooperative
Extension Service, the Division of Agriculture conducts research and extension work
within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas
System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.
The University of Arkansas System Division of Agriculture offers all its Extension
and Research programs to all eligible persons without regard to race, color, sex,
gender identity, sexual orientation, national origin, religion, age, disability, marital
or veteran status, genetic information, or any other legally protected status, and
is an Affirmative Action/Equal Opportunity Employer.
# # #
Media Contact: Fred MillerU of A Division of AgricultureArkansas Agricultural Experiment Station(479) email@example.com