SOYBEAN RUST: How should you plan for it?


SALEM, Ohio – Farmers may not be gearing up for harvesting season, planting season or tilling season yet, but they are in the middle of “planning” season. And this is the first year farmers will be shaping all their seasons around soybean rust.
Asian soybean rust hit nine southern states last fall, marking the first time the disease has been found in the U.S. mainland. It remains to be seen, however, whether it will creep to the Midwest this year.
But with a disease that claimed up to 80 percent yield losses in areas of South America, U.S. experts aren’t taking any chances.
What exactly is soybean rust and what does it mean to you?
Soybean rust attacks a plant’s leaves, causing it to rapidly defoliate and fail to produce pods, meaning the yield is slashed. Wind carries these spores throughout the field and to other farms and states.
In fact, soybean rust probably blew into the United States from South America on the winds of hurricanes Frances and Ivan, said Penn State plant pathologist Erick DeWolf.
Experts predict soybean rust could cause a 50 percent yield loss in the southern United States where it’s warmer, and more than a 10 percent loss in other areas, including Ohio.
The USDA estimates losses will range from $640 million to $1.3 billion, depending on when and where soybean rust strikes. If it hits late in the season, the seed would already be formed and the impact minor. However, if it comes when the plant begins flowering, the loss could be more significant.
Whether it will move north this year depends on the winter’s severity, DeWolf said.
Soybean rust is not likely to survive the harsh conditions in Ohio and Pennsylvania, but it can survive the warmer Gulf Coast and Caribbean regions and could be reintroduced each year.
It’s definitely a threat that’s here to stay, DeWolf said.
What are your options?
So far, there aren’t any resistant soybean varieties, so farmers are left to other means for dealing with this disease.
Fungicide. “Fungicides are likely going to be the first line of defense over the next few years until breeders can develop resistant varieties,” DeWolf said.
The primary time to protect plants from soybean rust with fungicides is during flowering and pod development.
These are the times when soybean rust will have the largest impact, said Ohio State plant pathologist Anne Dorrance.
But there’s more to learn about fungicides, especially when many soybean farmers in the Midwest aren’t used to applying a foliar fungicide.
Farmers will need help determining a correct nozzle size and operating pressure to get medium-sized droplets.
“Spraying the right amount of fungicide is not enough to achieve effective control. The single most important factor affecting the outcome of the fight against this disease is to get a thorough coverage of the plant with the fungicide,” said Ohio State ag engineer Erdal Ozkan.
“We have the technology to achieve this, but it may come with a higher equipment cost,” he said.
Switch to corn. Switching your soybean acreage to corn is an option, too, DeWolf said.
But it depends on the land.
If your soybean acreage is marginal ground and not at or above the state average in yields, it wouldn’t financially support the fungicide applications necessary to fight soybean rust, DeWolf said. In this case, consider switching to corn.
Wider rows. Some experts are advising farmers to use wider rows so more fungicide can reach the plant.
But DeWolf says farmers use narrow rows for economical reasons: higher yields and that’s what their equipment is made for.
Unless farmers can afford to buy the necessary equipment for wider rows, he doesn’t recommend the switch.
Dorrance agrees: “If Ohio is going to remain competitive, we are going to have to learn to manage rust in our high-yield production systems that we currently have in place.”
Drop seeding rates. Dorrance, however, does recommend dropping seeding rates.
“We know that we overplant in Ohio and seed costs continue to rise, so maybe this is the year to shoot for 180,000-200,000 seeds per acre instead of planting 250,000 or more,” she said.
“The seed quality is higher than last year and the seed is much bigger, so this will be a good year to try this.”
Crop insurance. Getting insurance is one way to protect your revenue, according to crop insurance agents Dale Hamilton of Carrollton, Ohio, and Alan Moser of Minerva, Ohio.
Peril crop insurance policies cover soybean rust just like any other disease, and diseases are a covered loss, Moser said.
Farmers, however, are still expected to exercise good farming practices, Hamilton said.
They must be monitoring their fields and taking precautions or else their claims could be turned down, he said.
The deadline to apply for crop insurance is March 15.
Scout and send. Be vigilant about scouting your fields, DeWolf recommended.
Do your homework so you know the symptoms when you see them.
And, at first sight, get samples of 20-30 leaves and send them to your state’s testing clinic. There are many look-alike diseases, such as downy mildew and brown spot, but if in doubt, still mail samples.
The key to controlling soybean rust, DeWolf said, is to catch it early.
Prepare. Before you’re faced with soybean rust in your fields, make some decisions, DeWolf said.
How will you respond if you discover you have soybean rust? Will you use fungicides? Do you know what fungicides are available?
And how will you afford fungicide applications? Do you need to decrease spending in other areas so your wallet is ready? Experts anticipate fungicide treatments may cost farmers as much as $25-$35 per acre.
Leave it in their hands. As long as you’ve taken precautions and your farm is prepared for soybean rust, leave the rest of the worrying to the experts.
A series of “sentinel” soybean plots will be planted across Ohio, said Ohio State plant pathologist Pat Lipps.
The fields will be planted early so that if soybean rust spores blow into the area, these will be the first spots to show the symptoms.
Then experts can warn the rest of the state’s growers, Lipps said.
(Reporter Kristy Hebert welcomes feedback by phone at 800-837-3419, ext. 23 or by e-mail at

Related stories previously published:
Soybean rust confirmed in U.S. (11/18/2004)

Related links:
Ohio State:

Animal and Plant Health Inspection Service:

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