Washington, DC
November 10, 2004
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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.
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Soybean rust pustules under a 20X magnification.
Source:
University of Nebraska Lincoln
- Crop Watch |
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" Web site at
http://www.aphis.usda.gov/lpa/issues/sbr/sbr.html. |
