WASHINGTON, Nov. 10, 2004 – The U.S.
Department of Agriculture’s
Animal and Plant Health Inspection Service today confirmed
the presence of
soybean rust on soybean leaf samples taken from two plots
associated with a
Louisiana State University research farm Saturday.
While this is the first instance of soybean
rust to be found in the
United States, the detection comes at a time when most soybeans
have been
harvested across the country. As a result of the harvest,
the impact of the
fungus should be minimal this year.
Soybean rust is caused by either of two
fungal species, Phakopsora
pachyrhizi, also known as the Asian species, and Phakopsora
meibomiae, the
New World species. The Asian species, the one found in Louisiana,
is the
more aggressive of the two species, causing more damage
to soybean plants.
USDA will dispatch its soybean rust detection
assessment team,
composed of scientific experts and regulatory officials,
to the site within
24 hours. The assessment team will work closely with Louisiana
State
Department of Agriculture representatives to assess the
situation and
conduct surveillance around the detection site to determine
the extent of
the disease spread.
Soybean rust is spread primarily by wind-borne
spores capable of
being transported over long distances. At this point in
time, based on
predictive models, APHIS believes that the detection in
the U.S. is related
to this year’s very active hurricane season. While
the harvest for this
year is complete, during next year’s planting season,
producers will need
to watch for symptoms of the fungus such as small lesions
on the lower
leaves of the infected plant that increase in size and change
from gray to
tan or reddish brown on the undersides of the leaves. USDA
and the soybean
industry have been cooperating on awareness efforts and
will amplify those
efforts now that the disease has been found in this country.
Lesions are
most common on leaves but may occur on petioles, stems,
and pods. Soybean
rust produces two types of lesions, tan and reddish brown.
Tan lesions,
when mature, consist of small pustules surrounded by slightly
discolored
necrotic area with masses of tan spores on the lower leaf
surface. Reddish
brown lesions have a larger reddish brown necrotic area,
with a limited
number of pustules and few visible spores on the lower leaf
surface. Once
pod set begins on soybean, infection can spread rapidly
to the middle and
upper leaves of the plant.
Soybean rust can be managed with the judicious
use of fungicides.
However, early detection is required for the most effective
management of
soybean rust. Monitoring soybean fields and adjacent areas
is recommended
throughout the growing season.
Fungicide applications can reduce yield
loss, depending on the plant
developmental stage, time when soybean rust is detected,
and fungicide
application method. Efficacy information for producers on
fungicides is
available through state university extension services.
For more information, visit APHIS’
soybean rust “hot issues” website at www.aphis.usda.gov/lpa/issues/sbr/sbr.html.
