Soybean rust may have slipped from the high profile radar screen for many involved with soybean production, but this disease remains a potential threat to soybean production in Minnesota. Whether it is a large or small threat, and whether or not soybean rust will be seen in Minnesota in 2006 is unknown – but the damage this disease can cause is too great to be unprepared for its possible arrival in Minnesota. The Minnesota Soybean Rust Task Force, which is composed of a diverse group of representatives from the U of Minnesota, Minnesota Soybean Research and Promotion board, Minnesota Department of Agriculture (MDA), crop consultants, and others has continued working to prepare and plan for soybean rust. This article provides a brief update on soybean rust in the U.S. and what preparations have been made to monitor and manage soybean rust in Minnesota.

In the U.S. this spring the status of soybean rust has been nearly static for almost two months. Locations where active soybean rust has been confirmed are limited to Florida, Alabama, and Georgia where soybean rust has been found primarily on kudzu. Soybean rust has been detected on soybeans only in one sentinel plot in southeastern Florida. It appears that most or all of the infected sites known to date in 2006 were also overwintering sites, and there is very little evidence that soybean rust is spreading to any significant degree yet this spring. Observers in southern states have suggested that dry weather conditions may be limiting movement and development of soybean rust in 2006. If we think back to 2005, however, there was little spread of soybean rust until late in the season. As of mid June 2006, the risk appears to be low for soybean rust developing in Minnesota in the foreseeable future.

Last year in the southeastern states where soybean rust developed (and caused significant yield losses in some areas), sentinel plots were often the first locations where soybean rust was detected in a area. For this reason an extensive network of soybean rust sentinel plots has been established in many states, including Minnesota. Minnesota has 25 sentinel plots in 2006 located in the following counties: Blue Earth, Dakota, Freeborn, Goodhue, Houston, Jackson, Marshall, McLeod, Nicollet, Nobles, Norman, Olmsted, Otter Tail, Pipestone, Polk, Ramsey, Redwood, Renville, Sibley, Stearns, Stevens, Swift, Waseca (2), and Wilkin. Supported by funds from USDA, the North Central Soybean Research Program, and the Minnesota Rapid Agricultural Response Fund, these plots will be scouted and sampled weekly. Leaf samples will be sent for analysis to a central laboratory on the U of Minnesota campus in St Paul. Last year, close examination of leaves with a stereomicroscope was found to be important for early detection of soybean rust in the southeastern U.S., and this approach will be used widely this year. Results from the sentinel plots in Minnesota and other states will be reported regularly on the USDA soybean rust USA web site (www.sbrusa.net). This site provides timely updates on soybean rust occurrences in the U.S. as well as commentaries by plant pathologists from each participating state.

Although the sentinel plots provide an excellent way to monitor development of soybean rust, a long-term goal is to develop methods to detect spore movement and to forecast soybean rust development before disease actually develops in sentinel plots or commercial fields. With this goal in mind, several types of spore traps are being tested in Minnesota. One of these 'traps' revealed that soybean rust spores were being transported to southwestern MN last July, even though soybean rust disease did not develop in Minnesota or other states in the upper Midwest last year. This illustrates that it takes more than the presence of the pathogen to initiate this disease: there must also be wet conditions and a sufficient number of spores introduced into a field. Please see another recent article in Minnesota Crop E-news that provides more information on the soybean rust spore trapping efforts in Minnesota. Information from spore traps as well as weather and crop development information is also being used to develop soybean rust forecasting tools. These are under development, but may be of great help to producers working to prepare for and manage this disease if it arrives in Minnesota.

Management of soybean rust will depend on foliar fungicides this season and probably for at least several years into the future. A number of different fungicides are available in Minnesota, many with section 18 emergency registrations, to manage soybean rust. In addition to the fungicides that were available in 2005, several new fungicides have recently received section 18 approval in 2006. These include Alto (active ingredient is cyproconazole) from Syngenta, as well as Caramba (active ingredient is metconazole) and a co-pack of Caramba and Headline (active ingredient is pyraclostrobin) from BASF. For a complete list of all section 18 fungicides available in Minnesota for soybean rust management, please see the MDA web site (www.mda.state.mn.us/appd/pesticides/fifra18.htm). There are also currently three fungicides with full section 3 labels for management of soybean rust and other foliar diseases of soybean. These are Headline, Quadris (active ingredient is azoxystrobin), and various formulations and products containing chlorothalonil. The other related new and useful item for 2006 is fungicide trial evaluation data from the U.S for soybean rust management. Trial data from Georgia, Florida, and Alabama, as well as from other countries, has been published in 'Fungicide and Nematicide Tests', and can be found at this web site (www.plantmanagementnetwork.org/pub/trial/fntests/vol61).

The last item I will address in this article is a list of web sites that are good sources of information pertaining to soybean rust. This is not a complete list, but it provides examples. In addition to the USDA soybean rust USA web site and the MDA web sites noted above, the Plant Management Network (www.plantmanagementnetwork.org/infocenter/topic/soybeanrust), University of Minnesota "MN Soybean Just for Growers" (www.soybeans.umn.edu/home.htm), and Plant Health Initiative (www.planthealth.info) web sites provide much information on soybean rust as well as links to other useful sites. While we cannot yet predict when, where, or how severely soybean rust may develop, we can prepare well and be well informed to minimize potential losses from this disease.

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