story to find out more.
bean leaf showing pustules (fruiting structures) of the bean rust fungus. Each
pustule contains thousands of fungal spores. Click the image for more
information about it.
Scientists Help Rust-Proof America's
Soybeans By Jan
Suszkiw June 2, 2006
Fungicides are a key frontline defense against Phakopsora
pachyrhizi, the latest fungal threat to Americas soy crop. Many of
the fungicides approved for use against this exotic fungal pathogen owe their
availability to the efforts of Agricultural Research Service (ARS) scientists in Urbana, Ill., and Fort
First detected in Louisiana in November 2004, the fungal disease
called soybean rust has since been found in 11 other states. Two years before
its arrival, though, ARS researchers
Miles were already busy coordinating field trials of tebuconazole,
tetraconazole, myclobutanil and trifloxystrobin plus propiconazole in
rust-infested regions of Zimbabwe and South America.
There, they examined fungicide timing, application methods and rates,
efficacy and residual activity. That and other data expedited approval of state
requests for emergency-use exemptions for the fungicides on soybeans from the
U.S. Environmental Protection Agency, under
section 18 of the Federal Insecticide,
Fungicide and Rodenticide Act.
At the Biosafety
Level-3 Plant Pathogen Containment Facility at Fort Detrick, molecular
biologist Reid Frederick (left) rates plants for resistance to Asian soybean
rust while plant pathologist Monte Miles inputs the data on a laptop computer.
Click the image for more information about it.
Key findings included showing that all of the fungicides studied by
the ARS scientists reduced soybean rust severity, although their effectiveness
and residual activity varied. Some, for example, worked better than others when
rust was severe, according to the researchers.
Frederick, a molecular biologist, is in the ARS
Disease-Weed Science Research Unit at Fort Detrick. Hartman and Miles, both
plant pathologists, are with the ARS
Germplasm, Pathology and Genetics Research Laboratory in Urbana. Since
2003, theyve examined more than 30 active ingredients representing both
single and dual-active fungicides, according to Miles.
The researchers caution that fungicides are a short-term solution to
the problem. Over the long term, the battle against soybean rust will require a
combination of strategies, with disease-resistant soybean cultivars as the
cornerstone. Other ARS teams, meanwhile, are examining other aspects of
fungicide use, including the influence of soybean planting dates, row spacing
and maturity groups.
about the research in the June 2006 issue of Agricultural Research
ARS is the U.S. Department of
Agricultures chief scientific research agency.