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Soybean Diseases




Asian soybean rust (SBR) was found in the southeast USA on soybeans in the spring of 2005 and has also been reported on Kudzu. Epidemics of rust for 2005 will now depend on weather conditions during the soybean growing season. Spread of rust will also be determined primarily by weather conditions and the concentration of soybeans planted in an area.

1. There is a national rust monitoring system in place for the United States. You can now log on to a web site and see where rust is currently reported in the USA and where it has not been found based on ground scouting of fields. This site is updated often, so the movement of rust in the US soybean crop and its spread up toward North Dakota can be monitored and viewed on the internet. This is where you can tell if soybean rust is in your region or getting close. Go to this official USDA web site and then in the lower center portion click on " USDA public soybean rust web site. Track the movement of SBR in the United States". This will take you to a map of soybean rust in the US. (instructions on how to use this map )

2. There is also a soybean rust forecasting system that predicts if soybean rust spores will move from areas with rust to areas without rust. This system can also predict if the weather conditions will be conducive to infection and disease development. This will indicate if rust spores could be moving into the North Dakota region. This is the North American Plant Disease Forecast Center web site: Once in this site, notice the section Epidemic Update. This gives a synopsis of the soybean rust epidemic in the US. Then there is a link to Current Forecast. This is what you would look at to find out if there is a chance that rust spores would be blowing up into the Dakotas and if the weather conditions would be conducive to disease development in our area.

2. Soybean rust is controlled only through the diligent use of fungicides. All soybeans are susceptible to rust. If there is no rust in our region or if there is no evidence that rust spores are going to be introduced, there will be no reason to apply fungicides. Remember, current scientific evidence indicates that fungicide applications should begin at the beginning of flowering (R1 stage) and not before and should not be applied after R6. Excellent information on fungicide use is now available at this web site: FUNGICIDE USE

This web site will give you information on North Dakota pesticide labels: PESTICIDE LABELS

Further information on rust control will be found at: Dr. Carl Bradley's Web Site


Instructions on using the USDA map monitoring the movement of soybean rust: When you log onto this site a United States map (with states outlined) of the scouted field sites and the sites with confirmed soybean rust will appear at the center of the page. At the bottom of the center map the color bars indicate scouted fields and rust fields confirmed. To move around in this map notice the magnifying glasses on upper left side. If you click on the Zoom Out or Zoom In icons, you then go to the map and each time you click on the map, you will zoom in the direction you chose. If you click on the 4 way arrows icon, then you can pan around in the map by clicking on one of the 4 sides of the map and the map will pan in that direction. The world icon on that top menu bar is a Full Extent screen which brings you back to the full map of the United States. There is also a refresh icon (two arrows in a circle).

Notice the smaller maps off to the right side titled Observation, Scouting and Disease Management. The top one, Observation, is the one that the program defaults to when you first log on and will be the most useful to see where rust is reported. Notice that the name Observation is highlighted when you are on that map. To look at the other two maps, just click on the title name and it will appear in the center area.

On the left hand side of the center map are the dates that data is recorded for SBR. You can go back to a previous date to see where rust was reported at that date. Just click on the date. Be sure you are already on the Observation map window.



Dr. Carl A. Bradley, Extension Plant Pathologist, North Dakota State University

NOTE: Asian Soybean rust was discovered in November of 2004 in Louisiana, Mississippi, Florida, Alabama, Georgia, Arkansas, Missouri and South Carolina. (http://www.aphis.usda.gov/lpa/issues/sbr/sbr.html).

NDSU will keep growers advised of any new developments in rust management techniques and rust occurrence in our area. Remember, it will not be necessary to apply fungicides if there is no rust in your field/area or if environmental conditions are not favorable for disease development. Scientists do not know how long it will take for rust to reach our northern area, but it could arrive within a single growing season. Growers should be aware that bringing in farm equipment from areas with soybean rust might also bring the rust spores into their farming operations.


1) What causes soybean rust?

Soybean rust can be caused by two different rust fungi: Phakopsora pachyrhizi and Phakopsora meibomiae. Of the two pathogens, Phakopsora pachyrhizi causes the most economic damage and is known as "Asian soybean rust".

2) Will soybean rust be able to survive the winters of the northern United States?

In Asia, soybean rust is able to overwinter between the 20th and 30th parallels. In the U.S., the 30th parallel runs along our very southern states along the Gulf of Mexico. It is unlikely that soybean rust will be able to overwinter in the northern United States.

3) Can soybean rust survive on the seed?

Soybean rust is not a seedborne disease and cannot survive on soybean seed. However, it may be possible that soybean rust could survive on infected pod or leaf tissue that could be mixed with seed.

4) Will soybean rust affect northern soybean production states like North Dakota and Minnesota?

Soybean rust may be able to blow up to the northern states during the growing season and cause infections on soybeans growing there.

Rust pustules on a soybean leaf. Courtesy of Dr. Glen Hartman.

5) Where can Asian soybean rust currently be found?

Asian soybean rust can currently be found in Asia, Australia, Africa, South America, and Hawaii. It was reported in Louisiana, Mississipi and Florida in the fall of 2004.

6) What other plants are hosts for soybean rust?

Soybean rust can cause infection on several legume plants which include dry edible beans, some ornamental plants, and kudzu, which is a weed present in the southern U.S. We do not at this time know how soybean rust will affect the dry bean or other legume crops in ND.

7) What management options are available?

Currently, there are no commercial soybean varieties with resistance to soybean rust. Fungicides will be the primary method of control. Currently, the fungicides Quadris and chlorothalonil (Bravo, etc.) have a label for soybean rust control in the U.S., and 4 other fungicdes have section 18 exemptions. Additional fungicides are pending approval.

The use of fungicides, which are to protect the leaves from infection, will require the early detection of rust in a field or area. Therefore, being able to identify soybean rust is critical to managing this disease. Unfortunately, in the early stages of disease development, rust can resemble a few other soybean diseases, therefore, it is more difficult to correctly identify compared to rust diseases on other crops, such as dry beans and wheat that many growers recognize.

8) What do I do if I suspect that I have soybean rust?

The USDA has established a protocol for verifying the introduction of soybean rust into a state, but his may change if it becomes widespread. If you suspect soybean rust has affected your soybean field in North Dakota, collect affected leaves (at least 20 leaves ) in a sealed plastic bag, and send them immediately to the NDSU Plant Diagnostic Lab. If soybean rust is suspected by the NDSU Plant Diagnostic Lab, then samples will be sent to a plant pathologist at the USDA-APHIS for confirmation. Contact information for the NDSU Plant Diagnostic Lab is as follows: Mailing Address: NDSU Plant Diagnostic Lab, 306 Walster Hall, Box 5012 Fargo, ND 58105, Tel: 701-231-7854, Fax: 701-231-7851. E-mail:diaglab@ndsuext.nodak.edu

9) Where can I find more information about soybean rust?

More information on soybean rust can be found on the following links:












>Phytophthora root rot
>Sclerotinia stem rot
    (white mold)
>Soybean Cyst Nematode
>Rhizoctonia root rot
>Fusarium root rot
>Sudden Death Syndrome
>Seedling and seed rots
>Bacterial blights
>Downy mildew
>Brown stem rot

>Disease Management
>Seed Treatments


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Prospective students may schedule a visit by calling 1-800-488-NDSU.
E-mail: Berlin D. Nelson
Department of Plant Pathology
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Walster Hall, Room 305
Fargo, ND 58105
Tel:(701) 231-7057 Fax:(701) 231-7851