| WASHINGTON, Nov.
10, 2004, USDA: 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, this is not a viable option
for most organic farmers. If you are growing organically
your best bet is to focus on prevention until more research
into biological controls has been done. Select varieties
that have shown some resistance to the disease. Early
detection is required for the most effective management
of soybean rust. If you find rust on a single plant
remove the plant, roots and all, place it in a plastic
bag and dispose. If caught early enough this may keep
the disease from contaminating the rest of the field.
Once rust has been identified contact your extension
agent for the latest developments. Monitoring soybean
fields and adjacent areas is recommended throughout
the growing season.
Since rust has not affected farmers in the U.S. little
research has been done on the disease and little is
known about treatment methods, resistant varieties and
preventative practice. However with the disease now
an eminent threat it is likely many more research dollars
will be spent learning how to control it. Expect a flood
of new information in the coming months and years.
For more information, visit APHIS' soybean rust "hot
issues" Web site at http://www.aphis.usda.gov/lpa/issues/sbr/sbr.html.
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