Fungicides are a key frontline defense against Phakopsora pachyrhizi, the latest fungal threat to America's 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 Detrick, Md.

ARS researchers have 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.

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.

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.

Read more about the research in the June 2006 issue of Agricultural Research magazine, available online at:

http://www.ars.usda.gov/is/AR/archive/jun06/beans0606.htm