Asian rust in soybeans and influenza in humans may not appear to have much in common. But if you're struggling sorting through treatment options for Asian rust in soybeans, think about how a flu shot works in humans.

"You need to get a flu shot before flu season starts," says Marilene Iamauti, a field research and development leader in Brazil for Dow AgroSciences. "After you have the flu and have all the symptoms, it doesn't matter if you get a flu shot then."

Iamauti told a standing-room only crowd at a January 25 agronomic update meeting in Council Bluffs, Iowa, the same principle applies to Asian rust. "You need to protect the crop before you have the symptoms," she says.

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As you begin to think about how to deal with this disease, get used to the terms "curative" and "preventive". The curative approach deals with treatments after a plant is infected. Curative treatments can curb an infestation, but only if a fungicide is applied after the spores that trigger Asian rust arrive during a three-day latent period and a subsequent four-day infectious period, says Iamauti. No visible symptoms surface during this time. When the main symptom of Asian rust - leaf lesions - appear approximately 20 days later it's too late to effectively treat.

Preventive treatments occur when fungicide is applied to a field before spores land. Iamauti says preventive fungicide applications provided the most reliable control in 52 trials over two years in the main areas of Brazil's soybean belt.

However, spending up to $25 per acre on one fungicide application is a sizeable investment, particularly if Asian rust doesn't infect a region. (One farmer during a break half-jokingly muttered he was placing his order for corn.)

Instead of scouting for symptoms in fields, much of the scouting for Asian rust will be done on the Internet, says Bob Gordon, senior fungicide marketing specialist for Dow AgroSciences. Gordon advises Midwestern farmers to watch weather patterns this winter in southern states for warm, moist conditions that favor development and spread of the spores. The planting of sentinel plots also will be completed across many states later this year. They'll enable researchers to track the spread of the disease during the growing season and post it on the Internet.

"Sentinel plots planted in your state are not for you," said Gordon. "The ones downwind from you are the ones you need to watch. Your first line of defense is watching what's happening 500 miles away." Should the disease begin moving northward your way, you need to be prepared for treating the disease, he adds.

"Listening to all these questions (at the meeting) is like listening to growers in Brazil two and three years ago," says Iamauti. "At that time, we never knew it would be this devastating, but we do have lots of experience with it."

StopSoybeanRust.com is a Web site with information and resources about Asian soybean rust, created by the Greenbook, Dealer & Applicator magazine and Successful Farming magazine. It is sponsored by Bayer CropScience US. Content is provided by a variety of sources including the United Soybean Board and the Crop Advisor Institute.