Fayetteville, Arkansas
November 21, 2007
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Ph.D. student
Valeria Avanzato of Buenos Aires, Argentina,
selects Fusarium isolates from a collection of
pathogens maintained by the University of
Arkansas Division of Agriculture for research of
soybean seedling diseases. |
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Fungicide seed treatments offer
protection from seedling diseases that can reduce soybean stands
and reduce yields, said John Rupe, plant pathologist for the
University of Arkansas
system's statewide Division of Agriculture.
Rupe said three groups of pathogens cause seedling diseases in
Arkansas: Pythium, Rhizoctonia and Fusarium. Pythium has five
different species that cause disease in Arkansas. Division
scientists are still identifying the Fusarium species
responsible for disease. Only one Rhizoctonia species,
Rhizoctonia solani, is known to cause disease in the state.
Rupe said three years of research data can help producers know
which fungicides are most effective for seed treatments.
Division scientists have tested nine commercial fungicides at
three planting dates in April, May and June. The tests were
conducted at three locations on research and extension centers
at Keiser, Stuttgart and Hope. Both high quality and low quality
seeds were included in the tests, Rupe said.
Test plots with treated seed showed significantly better
seedling stands than untreated control plots at some or all of
the planting dates at each of the research sites.
The research demonstrates that fungicide seed treatments can
improve stands and often yields with both high quality and low
quality seed that’s planted in a variety of environments and
locations, Rupe said. This is especially important if growers
reduce the seeding rate to reduce planting costs.
“The improved stands and yields were seen mostly in seed planted
in April or June,” Rupe said. “Plant stress from being planted
in soil that’s either too cool or too hot seems to be having an
effect on the results.”
Rupe also said that broad-spectrum fungicides that control
multiple pathogens were more consistently effective in varying
environments than fungicides that control specific diseases.
“This suggests there are a number of different pathogens causing
seedling diseases in these locations,” he said.
Rupe also said low quality seed benefited more often from
fungicide treatments than did high quality seed, though both
high and low quality seed saw improved stands and/or yields in
many plots.
“The longer it takes a plant to emerge from the ground after
planting, the more vulnerable it is to diseases,” Rupe said.
“High quality seed gets out of the ground faster.”
In ongoing research, Rupe and graduate student Valeria Avanzato
are trying to narrow down which specific pathogens are attacking
the plants at the various planting dates, environments and
soils. Rupe said he is also working with soybean breeder Pengyin
Chen to screen cultivars and breeding lines for resistance to
Pythium.
“When we started this study three years ago, we believed Pythium
was the most important seedling disease we were dealing with,”
Rupe said. “In the seed treatment studies, broad spectrum
fungicides were more effective than fungicides that specifically
treated Pythium, indicating that other pathogens were also at
work in Arkansas fields.”
Rupe and Chen found one soybean variety that has resistance to
Pythium, and are taking a closer look at some others that they
believe may also have resistance.
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