UM Extension: Minnesota Crop eNews

May 18, 2005

Status of Asian Soybean Rust in the United States and Minnesota as of May 13th, 2005

David Nicolai, Regional Extension Educator-Crops, Hutchinson
Lisa Behnken, Regional Extension Educator-Crops, Rochester
Seth Naeve, Extension Specialist-Soybeans

Asian soybean rust continues to be of concern to soybean farmers in the United States and Minnesota, but the disease is at present restricted to the states of Florida and Georgia. Seminole County, (Southwestern) Georgia, is the latest county outside of Florida to report Asian soybean rust in 2005, according to the USDA Public Soybean Rust Web which reported it as of Wednesday, April 27th, 2005. This is also the first 2005 report of rust found on soybean plants -- the other three confirmations were found on kudzu (a weed in southern US) in three different counties in central Florida.

The risk to northern soybean production regions during this season still remains largely unpredictable. If the disease is found widespread in alternative hosts and volunteer soybeans in May in coast states including Louisiana, Mississippi, and Alabama, computer models indicate that spores of the fungus can reach northern production regions before July. The next few weeks are critical. Let's keep watching the USDA websites (listed below) for updates.

A number of efforts are being made to track soybean rust progress from one state, or region, to another.

1) Sentinel plots

Early disease detection efforts will be conducted across Minnesota and Iowa during the 2005 growing season. Field locations at greater risk for disease will be monitored closely. The sites will be scouted weekly and a number of lower-canopy leaves will be removed and examined during each visit.

Some sentinel plots will be located on public land, such as University experiment stations, while other ‘plots’ will be localized areas in much larger commercially-planted soybean fields. At this time there will be approximately 30 sentinel plots in Minnesota. In-field areas where plant leaves remain wet for extended periods (e.g., near tree rows, low spots or other protected areas) will also be scouted extensively.

2) North Carolina disease risk forecasting system website

Researchers at North Carolina State University are currently tracking weather system movement from areas identified to have spores of P. pachyrhizi in the US. The website provides information on weather systems and wind directions. It estimates the risks for high and low level air currents that might deposit rust spores in fields from infested locations up-wind. These efforts provide information on the risk for disease by identifying potential spore trajectories.

3) USDA soybean rust website

Plant pathologists and others from land grant universities, regulatory agencies, and private companies will submit data from disease detection and monitoring activities to the USDA. The information will be used to track disease progress of soybean rust in the US. Detection and monitoring efforts are already underway in Texas, Louisiana, and Florida and are illustrated on the website’s map. A small area within Florida has been colored red to indicate the location where diseased plant leaves were found. Results from other states are colored green to indicate that those locations were monitored, but the disease wasn’t detected.

There's now a link on the USDA Soybean Rust Website to "Sign Up For Alerts" about soybean rust. According to the brief, on-line sign-up form, "The USDA Soybean Rust e-mail notification system will send an e-mail alert each time new information about soybean rust is made available for the region and/or state you specified." Look for the link in the upper-right-hand corner of the Web page, in red type. The only identifier requested/required is your e-mail address, and you must choose a region.

Fungicides are licensed with the EPA and disease management recommendations are in place IF soybean rust becomes a production issue in Minnesota during 2005.

1) Section 3 and 18 fungicide registrations

A current list of approved fungicides along with spraying strategies can be found at the University of Minnesota soybean website, www.soybeans.umn.edu and the Minnesota Dept. of Agriculture at

Fungicides currently registered for Asian Soybean Rust in Minnesota include Full Federal Registration: Bravo WeatherStick, Echo 720, Echo 90DF, Quadris and Headline. Fungicides currently registered as Section 18 products for use include: Tilt 3.6EC, PropiMax 3.6EC, Bumper 41.8EC, Folicur 3.6 F, Laredo 25EC, Laredo 25EW, Domark 230ME, Stratego 2.08F, Quilt 1.66EC and Headline SBR.