Asian Soybean Rust 2006 Questions & Answers

What is Asian soybean rust?

Soybean rust is a plant disease caused by two fungal pathogens. Phakospora pachyrhizi, or the Asian type of rust, is the pathogen most commonly associated with soybean rust. The name can be somewhat misleading, because it has been found in Australia, Africa, South America and Hawaii, as well as Asia. As the most destructive pathogen, it poses the biggest threat to the U.S. crop. Phakopsora meibomiae, by contrast, is less aggressive and is not known to cause severe yield loss in soybeans.

How did Asian soybean rust reach North America?

It is suspected that Asian soybean rust spores arrived in the United States via Hurricane Ivan in September 2004.

How fast could Asian soybean rust spread?

Historically, it takes more than a month for an airborne crop disease to spread from the southern coast of the United States to Iowa, Ohio, central Illinois or central Indiana. Soybean rust was first detected in 2001 in southern Brazil. Because of Brazil’s tropical climate, the disease quickly spread, reaching the northern-most region by 2003.

Why didn’t Asian soybean rust spread like experts thought it would in 2005?

The outbreak and spread of Asian soybean rust is dependent on weather conditions. For disease to spread rampantly there needs to be three things: a host (soybeans or alternate host like kudzu), disease-carrying organisms (the Asian soybean rust spores, and environmental or weather conditions (moisture and temperature in the case of Asian soybean rust).

While spores were present in the U.S., particularly in the southern states, the initial spore load was low because frost during the winter killed kudzu from the Gulf Coast to central Florida. Also, spring and summer weather conditions conducive to spore germination and growth never occurred in 2005. Further, during the 2005 growing season, there was a severe drought and temperatures were warmer than normal. Since long periods of leaf wetness and temperatures between 60- and 85-degrees Fahrenheit with a high relative humidity of 75 -80 percent are needed for Asian soybean rust spore germination, the conditions were not conducive to Asian soybean rust spread in 2005. In fact, temperatures above 90 degrees Fahrenheit halt spore germination and growth.

What will Asian soybean rust disease pressure be like in 2006?

No one knows for sure, but there are some patterns worth watching. Weather conditions that favor development of the disease during the growing season will determine the severity of soybean rust this year. Temperatures were the warmest ever during the 2006 winter season. Many of the kudzu plants in southern states that tested positive for Asian soybean rust in 2005 did not die because temperatures did not get below freezing. In mid-May, Florida officials found soybean rust on kudzu in the northern part of the state. Although early spring was dry this year, late spring brought several days of rain, higher humidity and a lot of dew all which encourage disease. Because spores are carried by the wind, an active summer storm/hurricane season could move spores from southern states or Mexico into soybean-growing areas.

What can growers do to prepare for an Asian soybean rust outbreak?

Growers should monitor the movement of rust, especially as it nears their area and fields. Timely fungicide treatments are the only proven solution in Brazil and other countries where Asian soybean rust has been a major disease problem.

By including Headline® fungicide in a crop management plan, growers can maximize yield potential and also protect their soybean crop on a preventative basis from Asian soybean rust. To maximize the results of Headline fungicide where rust is not present in the field or area, BASF recommends an application rate of 6 ounces per acre during the R2 to R3 soybean stage.

How can growers monitor or track the spread of Asian soybean rust and know if it’s in the area?

Go to www.soybeanrustinfo.com and click on the Soybean Rust Mapping Tool showing information provided by Growth Stage® Consulting Inc. compliments of BASF. (Note: USDA data is also used to help track infestations and is represented in these maps.)

Growers can also get updates on their cell phones through the Soybean Rust Voice Message Alert System which is part of SoyRAP® – the Soybean Rust Advisory Program of American Soybean Association and Doane. BASF is proud to be one of the top sponsors of this program. The voice message alert feature will deliver timely soybean rust alerts for local areas directly to the cell phone of subscribers (or other phone numbers if preferred).

How can Asian soybean rust be managed once it’s present in a grower’s area or field?

If Asian soybean rust is detected in a grower’s area or field, Headline SBR fungicide should be applied, but only in states that have granted a Section 18 exemption for Asian soybean rust control to the product. (For a list, go to www.soybeanrustinfo.com and click on the Section 18 State Update at left).

An application of Headline SBR should be made only if monitoring indicates rust is present in your area or field. Headline SBR can be applied to vegetative through R6 stage soybeans. It provides curative rust control and long residual as well as preventative soybean rust control.

If Asian soybean rust persists in the field, a second application of Headline SBR can be used if there are more than 14 to 21 days to the R6 soybean stage (full seed, seeds fill pods at 1 of 4 uppermost nodes). Do not use an adjuvant in combination with Headline SBR if soybeans are growing under high stress conditions (i.e., hot, dry).

Retailers, crop consultants and/or applicators may make specific program recommendations different than those listed here based on an individual grower’s situation – soybean type, stage of growth, weather conditions and disease threat.

What’s the difference between Headline and Headline SBR fungicide?

Headline fungicide (pyraclostrobin) was registered for use in corn and soybeans by the Environmental Protection Agency in 2004. Headline SBR fungicide is a co-pack combining pyraclostrobin with a triazole (tebuconazole) for overall preventative and curative rust control.

Headline SBR was granted state Section 18 exemptions for Asian soybean rust in 2005. To view a list of states that have Section 18 exemptions for Headline SBR, go to www.soybeanrustinfo.com and click the Section 18 States Update at left.

In South America, a similar combination of pyraclostrobin and an effective triazole fungicide is the most effective and widely used program to control Asian soybean rust.

In which state does Headline SBR have a Section 18 exemption?

Headline SBR currently has a Section 18 exemption in Alabama, Arkansas, Colorado, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Virginia, West Virginia and Wisconsin. For the most current list of states where Headline SBR has been granted a Section 18 exemption, always consult www.soybeanrustinfo.com.

In which states does Caramba have a Section 18 exemption?

Caramba™ fungicide currently has a Section 18 exemption in Minnesota and South Dakota. Although it is anticipated that additional Section 18 exemptions may be forthcoming. For the most current list, always consult www.soybeanrustinfo.com.

Where can growers get Headline SBR?

Growers in areas where Asian soybean rust has been identified should consult www.soybeanrustinfo.com for a list of retailers in their area with availability of Headline SBR.

Are Asian soybean rust -resistant varieties of soybeans available?

No. There are currently no resistant soybean varieties available. All soybeans are susceptible to the potentially yield-devastating fungus.

For use when Asian soybean rust spores are present or predicted to be in your area, with valid Section 18 exemption approved by State and Federal Regulatory agencies.

For more information on Asian soybean rust and Headline SBR – including a complete list of states where Headline SBR has been granted a Section 18 exemption and a list of retailers in affected areas where Headline SBR is available – please consult the BASF website at www.soybeanrustinfo.com.