Home

Diagnostic Identification Labs

Virginia IPM

Virginia Cooperative Extension

Pest Management Guides

Links





Copyright Virginia Tech

Virginia Asian Soybean Rust
Disease Management

Keeping Ahead of Soybean Rust

Since Asian soybean rust can develop very rapidly when environmental conditions and crop stages are conducive growers are advised to stay informed of rust movement in the United States, environmental conditions and regional crop development stages conducive for disease development and Virginia's current recommendations. Virginia growers have several alternatives for accomplishing these recommendations:
  • check the Forecast and Tracking page of this website often during the growing season
  • sign up for this website's email alert
  • call the toll-free Virginia Soybean Rust hotline for updates and current recommendations (757-657-6450, extension 130)

Also, see information on the USDA-PIPE website below.

 
 
 
 
 
 
 
Courtesy Kitty Cardwell, USDA-CSREES Although early stages of Asian soybean rust are difficult to detect by examination in the field, growers are still advised to scout fields. Avoid checking only the perimeter of fields. Walk fields in a �W� or zigzag pattern, using different entry and exit points for each scouting event. Also, pay particular attention to low-lying and shady areas or portions of the fields with dense canopy cover;  these areas tend to accumulate moisture favorable for disease development. Also pay attention to areas where soybeans are yellowing.
Use a 20X hand lens to check leaves of differing maturities on plants (i.e. leaves from the plant's top, middle, and bottom). Initial infections usually begin on lower leaves and can be hard to detect. Hold leaves up to the sky to backlight them for visualization of early and hard to detect symptoms of Asian soybean rust.
 

 
Growers can also check the national USDA-PIPE website to monitor rust movement. Various useful information for soybean producers is also available at the USDA-PIPE website--ID/Scouting Tools (Soybean Rust ID Card and Soybean Rust Scouting Video) and a Good Farming Practices Documentation Tool.

 

Currently there are no soybean varieties with acceptable levels of resistance to Asian soybean rust. Therefore, applications of foliar fungicides are necessary to control Asian soybean rust.

National Rust Management Guidelines as listed on the USDA-PIPE website (See Soybean Reproductive Stages table (below):
Vegetative Growth Stages
Current data indicate that fungicide applications are not needed in the early vegetative growth stages. Spraying just prior to crop flowering (R1) may be prudent if disease is increasing. This is especially true for late-planted crops and/or very late-maturing varieties that may develop a large canopy before flowering.

R1-R5 Reproductive Stages
Soybean rust symptoms are most prevalent, and increase most rapidly, during crop reproductive growth stages. The first fungicide application should be made before rust has appeared on more than 2% of the leaves in the crop canopy. One, two, or three applications may be needed, depending upon what growth stage the disease is first detected and subsequent environmental conditions. Consecutive applications of either strobilurins or triazoles alone should never be made due to resistance concerns. Refer to fungicide labels for specific directions and restrictions.
R6 and later
Spraying at late growth stages is not recommended due to lack of yield response. In addition, many fungicides have days to harvest (preharvest intervals) or growth stage restrictions. Refer to fungicide labels for specific directions and restrictions.
Timing of foliar fungicides to control Asian soybean rust is critical. For help in making fungicide application decisions check current Virginia recommendations often, either on this website on the Forecast and Tracking page, subscribing to our Asian Soybean Rust Website Email Alert or by calling the Virginia Soybean Rust Hotline (757-657-6450, extension 103).
See the Fungicide Use Guidelines posted at the USDA-PIPE website (or open the pdf of the Fungcide Use Guidelines here) and the Soybean Reproductive Stages table below.
Data from USDA sentinel plots and other Virginia survey efforts, along with soybean rust disease forecasts from the North American Plant Disease Forecast Center, will be used by plant pathologists at Virginia Tech to decide when applications of foliar fungicides should be made to soybean crops in Virginia.
Soybean Reproductive Stages (R1 to R8)--Note: vegetative stages occur prior to bloom.
R1-R2 beginning bloom to full bloom
R3 beginning pod development
R4 full pod developed
R5 beginning seed development
R6 full seed development
R7 beginning maturity (i.e. one pod at mature pod color; 50% or more leaves yellow)
R8 full maturity (i.e. 95% pods at mature pod color)
For a detailed description of soybean vegetative and reproductive stages see Soybeans: Growth Stages at the Ontario Ministry of Agriculture, Food and Rural Affairs:

Proper Equipment and Application Techniques to Ensure Adequate Fungicide Coverage

Proper application of foliar fungicides is critical to Asian soybean rust control. Refer to the documents in the table below for specific recommendations.
Specific Equipment and Technical Recommendation for Applying Fungicides to Control Soybean Rust, Robert Grisso, P. E., Biological Systems Engineering, Virginia Tech
Asian Soybean Rust--Frequently Asked Questions VI: Sprayer and Nozzle Technology, Virginia Cooperative Extension Publication Number: 450-306 pdf htm  
Application equipment for effective control of Asian soybean rust pdf htm
Fight against soybean rust by calibrating your sprayer pdf htm
Proper spray equipment, technique keys to Asian soybean rust pdf htm
Q & A: Nozzle packages for Asian soybean rust pdf htm
Aerial applications rust control pdf
Nozzles and the corresponding pressure and travel speed ranges to achieve "medium" droplets at a 20" nozzle spacing and 20 GPA pdf
Twin nozzles configurations and the corresponding pressure and travel speed ranges to achieve "medium droplets at a 20" nozzle spacing and 20 GPA pdf
Nozzle selector guide (Note: there are six worksheets in this Excel spreadsheet--see tabs at bottom of Excel document) Excel file

Return to top

Fungicides 101

Fungicides for controlling Asian soybean rust have either protectant or limited curative activity. Protectants should only be used in a preventative program--before Asian soybean rust has been detected in an area.

Protectants, such as chlorothalonil, are only effective if applied prior to spore germination and infection. Strobilurins, such as axoxystrobin, are effective in halting spore germination and infection, but if applied after the plant pathogen has entered the plant tissue, are ineffective.

Triazoles, such as myclobutanil, have limited curative activity. They slow the progress of, and in some cases may stop, previously established infections. However, the first fungicide application should be made before rust has appeared on more than 2% of the leaves in the crop canopy.

Fungicide Resistance Development and What Growers Can do to Prevent Loss of Fungicidal Activity

When using triazoles, and particularly strobilurins, be aware of the potential for resistance development in the soybean rust population. To ensure that these fungicides retain their activity against soybean rust adhere to these guidelines:

  • Limit solo applications (e.g. applying a only strobilurin or only a triazole fungicide) to one application of a solo strobilurin and two solo applications of a triazole per growing season.
  • Do not apply consecutive sprays of fungicides in the same class (e.g. two consecutive sprays of a strobilurin or triazole). Instead, alternate fungicide classes during the season (e.g. Follow a strobilurin spray by a triazole spray.).
  • Do not skimp on product; use the rate recommended on the label.
  • Use a premixed fungicide product, containing both a protectant and curative. This allows more than a single mode of action against the rust and decreases the likelihood of resistance development.
  • Finally, growers should monitor fields after fungicide use. If resistance development is suspected, contact your county Extension agent and/or the fungicide vendor.

A number of fungicides have been granted an emergency exemption in Virginia through Section 18 of FIFRA. For the 2007 growing season a number of  fungicides previously with a Section 18 status have been granted full registration. Products listed in the table below can be used to control Asian soybean rust on soybean in Virginia. PDF files for fungicide labels, section 18 labels and modes of actions are included when possible. Labels may be obtained from product vendor.

Registered Fungicides
Brand Name Common Name Fungicide Class Manufacturer Product Label (pdf) Virginia Section 18 (pdf) Mode of Action (pdf)
Domark 230 tetraconazole Triazole Valent   n/a  
Tilt propiconazole Triazole Syngenta pdf n/a  
Propimax propiconazole Triazole Dow Agrosciences   n/a  
Bumper propiconazole Triazole Makhteshim Agan   n/a  
Quilt
 propiconazole+ azoxystrobin Triazole Syngenta pdf    
Stratego propiconazole + trifloxystrobin Triazole Bayer Crop Science pdf n/a  
Bravo Weatherstik chlorothalonil Chlorothalonil Syngenta pdf n/a pdf
Chloronil		 chlorothalonil Chlorothalonil Syngenta pdf n/a  
Echo 720 chlorothalonil Chlorothalonil Sipcam Agro pdf n/a pdf
Quadris azoxystrobin Strobilurin Syngenta pdf n/a pdf
Equus chlorothalonil Chlorothalonil     n/a  
Ballad Plus Biofungicide

Bacillus pumilus strain QST 2808

   Agra Quest pdf n/a  

Virginia Section 18 Fungicides
Brand Name Common Name Fungicide Class Manufacturer Product Label (pdf) Virginia Section 18 (pdf) Mode of Action (pdf)
Alto 100SL cyproconazole   Syngenta   pdf  
Quadris Xtra cyproconazole + azoxystrobin   Syngenta      
Topguard flutriafol Triazole Cheminova   pdf pdf
Caramba metconazole Triazole BASF   pdf pdf
Punch flusilazole Triazole Dupont   pdf  
Laredo EC myclobutanil Triazole Dow Agrosciences pdf pdf pdf
Laredo EW myclobutanil Triazole Dow Agrosciences pdf pdf pdf
Headline pyraclostrobin Strobilurin BASF Ag   pdf  
The up-to-date list of Section 18 products registered in Virginia should be available at the Virginia Department of Agriculture and Consumer Services website.

Be aware that the law requires that both a physical copy of the product label, plus the Section 18 Emergency Exemption Label, to be available on site during product application. For labels not available here, you may obtain labels from your chemical vendor or search and download most product labels and Section 18 labels at Greenbook. Registration at Greenbook is required, but the service is free.

Documents needed to substantiate best management practices or to file a crop insurance claim (Provided by the Risk Management Agency (RMA) on April 27, 2006)
These may include:

1. Data from local weather stations;

2. Published anecdotal records such as newspaper and magazine articles;

3. Farm Service Agency (FSA) reports;
4. Written recommendations from extension agents or other agricultural experts (see crop insurance policy for a listing of qualified persons);
5. Printed information from Federal, state, university or extension official websites;
6. Other published information (facts sheets, bulletins, newsletters, etc) from:

A. Land grant universities;

B. Cooperative extension service; or

C. Independent third parties such as farm advisors or crop consultants.
7. Contemporaneous records of planting, spraying, scouting, harvesting, sold or stored production and any other applicable farm practices such as journals, logs, etc. that contain the date the practice occurred and how it was carried out;
8. Contemporaneous journals, logs or notes of persons contacts, the date, and the information provided;
9. Chemical labels and brochures; and
10. Other records as determined necessary by the crop insurance company or RMA;
11. Copies of receipts for all inputs such as seed, spray material, custom spraying, etc. (anything that went into producing the crop).
Soybean Rust, Crop Insurance and, You--a brochure from the USDA Risk Management Agency that instructs growers with crop insurance on how to find and follo.w recommendations of  agricultural professionals and keep records of control methods taken. Crop losses due to failure to stay informed and follow recommendations of agriculture professionals and/or improper application of controls will not be covered.
Please link to the Asian Soybean Rust: Notes and Organic Control Options for Farmers at the National Sustainable Agriculture Information Service (ATTRA) for information on Asian soybean rust control options for organic soybean production.

Recommended Resources

UPDATED VERSION NOW POSTED Using Foliar Fungicides to Manage Soybean Rust is a comprehensive source of information on management of Asian soybean rust with fungicides. This full-color publication was prepared by soybean pathologists from 23 land grant universities, including Virginia Tech, plus USDA-ARS and contains numerous illustrations, photographs, maps, tables, and charts, as well as a glossary of terms and a list of sources for additional information. Information includes:

  • First finding of  soybean rust
  • Making fungicide decisions for managing soybean rust
  • Fungicide basics
  • Application basics
  • Aerial application tips for rust control
  • Using skip rows to facilitate late-season pesticide application
  • Similar diseases

Download chapters of the book or order the book at the website. Copies are also available through Virginia Cooperative Extension offices.

The results of 2006 fungicide trials on Asian soybean rust are available in Plant Disease Management Reports, Volume 1 (formerly Fungicide and Nematicide Tests) .  This resource is published annually by The American Phytopathological Society and is available through the Plant Management Network. Subscription or membership in PMN is required for viewing reports. These concise reports should be useful for growers, fungicide retailers, crop advisors, and extension agents.

Snap beans (Phaseolus vulgaris) are susceptible to Asian soybean rust. Information on symptoms, disease cycle, epidemiology, and management of rust on snap beans can be found in: 2005 Alert: Asian Soybean Rust Threat to Dry and Snap Beans (pdf).

Return to top

Virginia IPM | Virginia Cooperative Extension | IPM in the Department of Entomology | Nematode Assay Laboratory | Plant Disease Clinic | Weed Identification Laboratory | Insect Identification Laboratory