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Corn+Soybean Digest

ADVICE: When Rust Arrives

But American producers, once the disease hits, will not have to fight soybean rust alone. USDA's Animal and Plant Health Inspection Service (APHIS) already has a Soybean Rust Detection Assessment Team in place, with staff divided among regional offices at Raleigh, NC, and Fort Collins, CO.

¡°The team is composed of academic and research scientists who will report on site within 24 hours to provide confirmation of the disease,¡± says Bob Spaide, a senior program advisor with APHIS.

The APHIS team will help gather data about the fungus in the field and provide technical assistance to growers in controlling it. ¡°Our expectation is that, if we find soybean rust in an area, the disease will be pretty widespread,¡± Spaide says.

That means producers whose crops are affected, as well as those within a 200- to 300-mile radius, will likely need to start applying fungicides immediately, according to Bob Streit, an Iowa agronomist and crop consultant.


Fungicide application appears to be an effective method to initially control the soybean rust fungus. However, there are several hurdles yet to overcome.

¡°We aren't adequately prepared because fungicides are not usually applied to soybeans,¡± says USDA researcher Monte Miles. This means supply of chemicals is limited, the method, timing and number of fungicide applications is unclear, and costs could be prohibitive ¡ª some estimate it from $15/acre all the way to $55.

For instance, in the U.S. only two active compounds ¡ª azoxystrobin (Quadris) from Syngenta and chlorothalonil (Bravo WeatherStik and Echo 720) made by Syngenta and Sipcam Agro ¡ª are currently registered for control of soybean rust. South Dakota State University Extension plant pathologist Marty Draper says there are other cholorothalonil generic products on the market, but those manufacturers haven't listed soybean rust on their label yet.

Jim Peters, brand manager of fungicides with Syngenta, admits that limited supply can be a very real scenario. He says that if soybean rust infects the crop at the early reproductive stage and environmental conditions allow the disease to multiply and spread quickly, numerous fungicide applications may be needed. ¡°Because soybean rust isn't in the U.S¨E the compounds haven't been tested here, so we must bridge our knowledge from Brazil,¡± Peters adds.

That said, USDA's Miles and Glen Hartman are spearheading efforts on fungicide research. The first year of field trials in Nebraska, South Dakota, Mississippi, Louisiana and Illinois will evaluate aerial and ground applications to identify methods that effectively penetrate the soybean canopy.

Additionally, research trials are in progress in the southern region of Africa, Brazil and Paraguay to identify more chemical compounds that will be effective in controlling the disease. Miles reports some early success: ¡°We've found several compounds that control the disease symptoms, but we don't have enough information on their impact on yield protection.¡±

Efforts are also under way to secure Section 18 exemptions from EPA should soybean rust emerge in the U.S. These pesticide labels allow emergency uses for non-labeled chemicals under special circumstances, says SDSU's Draper.


With all these efforts, those involved feel confident American soybean producers will be able to battle this disease. Streit advocates that solutions will only come through a collaborative effort. ¡°This is a Western Hemisphere problem. We will benefit from working with South American researchers, and they will benefit from working with us and the fungicide companies,¡± he says.

He's also hopeful that, through the research being conducted, a comprehensive predictive modeling system will eventually be put in place. ¡°We need to track spore trap data, rainfall and dew amounts, and wind pattern maps. So, once soybean rust is here, we can put out bulletins about which region should be applying fungicides at a certain stage, and what the spray schedule needs to be,¡± Streit says.

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