Table
of Contents
AL,
FL report more rust
As
rust spreads, some spraying recommended in Southeast
Growers
in northern states told to "wait and see"
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Breaking
News
AL,
FL report more rust
With
new finds of Asian soybean rust and favorable disease
weather, soybean specialists are calling for intensified
scouting efforts for rust spores in the southeastern
U.S. over the next 5 to 7 days. For state by state
updates on soybean rust cases and fungicide
recommendations, visit USDA's Web site at www.sbrusa.net.
The most recent cases were reported Tuesday, August 9
with a rust find confirmed in Lee County, Florida on the
southwest coast and an August 8 announcement confirming
rust in a sentinel plot at the R5 growth stage in
Escambia County, Alabama.
"Escambia County is just north of Baldwin County so
it's close to the Gulf. It was on a research station
there," Auburn University professor and Extension
plant pathologist Ed Sikora said. He reported that 65%
of the plants in the plot had symptoms, though disease
severity was relatively low.
The Escambia County finding comes after earlier soybean
rust discoveries in the state's Baldwin County, Elmore
County and on the Auburn University campus. These latest
findings were among several new cases of Asian soybean
rust confirmed last week August 3 and August 5 in
Florida, Georgia, and Mississippi. The cases in Elmore
County, Alabama and Laurens County, Georgia are the
furthest north that soybean rust has been reported in
2005. The Pearl River County field in Mississippi is the
furthest west that rust has been found in 2005. The case
in Madison County, Florida was the first find in a
Florida commercial field.
According to USDA's Soybean Rust Information Site,
Alabama now has three counties reported positive with
rust; Florida has twelve; Georgia has seven; and
Mississippi has two. The site also predicts that new
reports for soybean rust are expected to continue within
states already reporting rust over the next week with
new reports now coming in almost daily.
With the weather forecast indicating extended moisture
through August 14, the soybean rust model predicts new
spore transport and depositions to extend from western
Florida, through Alabama, Georgia, into eastern
Tennessee and Kentucky, the Carolinas, and the
Mid-Atlantic states as far north as extreme southern New
York.
As
rust spreads, some spraying recommended in Southeast
As
the spread of soybean rust continues to pick up the
pace, Georgia Extension plant pathologist Bob Kemerait
is expecting more cases of rust to pop up in his state.
After the seventh rust case was confirmed in Georgia
last week, he said, "It's conjecture, but with the
weather we've had I expect it will be found in
commercial fields very soon. The growth stage we're at
and the widening distribution of the rust leads me to
believe that."
He added, "Development of the disease in Georgia
hasn't spread over a huge area, but conditions have been
right for it lately. We're seeing rust respond more
quickly than it has been."
In Alabama, Auburn University plant pathologist Ed
Sikora is also alerting growers in south and central
Alabama with fields in early to mid reproductive stages
that they are at high risk for soybean rust. In his
commentary posted on the USDA Soybean Rust Information
Site, Sikora said, "Weather conditions are very
conducive to infection from the disease, especially
where frequent/daily rain showers are occurring. Spread
of the disease within sentinel plots in Lee and Elmore
counties in east central Alabama has been rapid in the
last week, so slightly cooler temperatures during this
period may have had a favorable effect on disease
progress."
Sikora says because of the varied growth stages of
soybean fields in Alabama at this time, a general
fungicide guideline is difficult to provide. Instead, he
is making recommendations on a field by field basis,
when possible. Overall, he suggests growers in south and
central Alabama with fields in reproductive stages
should consider using a curative, or a curative plus
protectant fungicide combination as there is a high
level of risk from soybean rust at this time. Growers in
north Alabama at the R2-R3 stage should consider a
protectant or a protectant plus curative fungicide
combination as rust appears to be moving slowly
northward. He adds that growers in north Alabama beyond
the R5 growth stage do not need to apply a fungicide at
this time.
In Florida, the recommendation is that growers consider
spraying for Asian soybean rust as their plants approach
bloom. According to the data posted on the USDA Soybean
Information Site, this recommendation is being made now
because of: 1) recent positive findings on kudzu and
soybean in the panhandle 2) experience with rapid
disease increase on soybeans in the Marion County
sentinel plot 3) the continuing high humidity which
favors disease development 4) the bloom stage of the
state's soybean crop 5) and the possible involvement of
tropical storms Arlene and Dennis in distributing
spores.
Growers
in northern states told to "wait and see"
In
Tennessee, Kentucky, Indiana and other northern states
Extension specialists are telling their soybean growers
to take a "wait and see" approach before
spraying fungicides for soybean rust.
University of Tennessee Extension specialist Beth Long
reports there have been no soybean rust infections or
rust pustules found within the state. She says,
"Tennessee producers should be very watchful and
report any leaf lesions that might be soybean rust to
their local county agent or first detector person and be
ready to spray for rust should infected plants be
discovered in Tennessee or close in adjoining states. To
monitor soybean rust updates in Tennessee a hotline has
been set up at: 865-974-2392
In Indiana, Purdue University professor Greg Shaner also
reports no Asian soybean rust has been found on soybean,
kudzu, or any other host species in Indiana, and
sentinel plots continue to be scouted regularly. Shaner
says many fields are now in the seed development growth
stages (R5 to R6). He adds, "There is no reason at
this time to spray a fungicide on soybeans for rust
control. As the season progresses with no rust anywhere
near Indiana, the probability that rust will arrive in
time to cause damage decreases. If rust does arrive
later in August, then a fungicide treatment may be
required to protect yield, but treatment should be
deferred until we know rust is present in the state, or
very near, in order to receive the full benefit of
treatment."
Similarly, Don Hershman, University of Kentucky
Extension plant pathologist, says as of August 9, 2005,
no soybean rust has been detected in his state. He
acknowledges that three of ten spore traps located in
Kentucky have had positive finds recently with rust-like
spores. But he stresses, "These spore finds should
not be cause for alarm. The spores may or may not be
those of the soybean rust fungus. As with past spore
finds, these new spore finds may have little or no
bearing on the soybean rust situation."
He adds, "If the recently found spores were, in
fact, those of the soybean rust fungus, it will take 3-4
weeks before there is enough rust to be visually
detectable. In my opinion, it is very premature to think
about spraying for soybean rust. Spraying now may result
in the need for a second spray in late August when a
fungicide application may be truly necessary. Until
there is some evidence that the risk of soybean rust in
Kentucky is high, it is suggested that the spray rig
remain in the barn and your money in the bank."
To monitor the status of soybean rust in Kentucky, check
their toll-free hotline at 1-888-321-6771.
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