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Soybean rust is real risk, but manageable

TUNICA, MISS. — Harold Lambert is one ag consultant who thinks that farmers’ potential plight with Asian soybean rust may not be as tough as some fear.

If his predictions prove true, farmers will have two major things to be grateful for: lessons from experienced Brazilian farmers and their own careful preparation for the windblown disease.

“I don’t believe the soybean rust threat for us here in the Mid-South will ever be as severe as it is in Brazil,” Lambert said.

Instead, Lambert, who recently returned from touring Brazilian farms where growers constantly cope with the disease, thinks other established soybean diseases — such as frogeye leafspot and cercospora leaf blight — could be bigger production obstacles over the next five years.

While Mid-South winter seasons are generally mild, most if not all South America soybean-producing areas have no winter weather to speak of, and that distinction, Lambert pointed out in a conference held recently in Tunica, Miss., is a pivotal difference when it comes to the life of soybean rust disease.

The malady is hampered in cold weather but thrives in temperatures ranging between 59 degrees to 77 degrees.

“We have a winter, they don’t have a winter. In Brazil, they are growing soybeans all year; across the landscape you have almost every conceivable growth stage out there. They have much dustier conditions behind the combines, and the air seems fill with a lot of spore inoculums,” he said.

Consequently, Lambert is optimistic that any presence of soybean rust in the United States can be effectively managed.

But that doesn’t mean growers can afford to be relaxed.

When the rust disease first surfaced in Brazil a few years ago, many farmers’ attitudes were skeptical at best, and Lambert cautioned that U.S. soybean farmers should not fall into that trap.

“In regard to farmers not wanting to change, they need to talk to some farmers in Brazil. They changed,” he said. “They changed or they went broke. When it comes to operating your business like it needs to be operated, you change or you’re out of it.”

Boyd Padgett, Extension agent with Louisiana State University, was also a visitor on the same group tour with Lambert.

Padgett, speaking separately at the same conference, emphasized that consultants must convince growers that having a vigilant attitude toward the disease is imperative. He said producers in South America take few if any chances on the disease, which is elusive and aggressive.

Padgett said a group of employees on one of the largest soybean farms in Brazil scout for the disease every two days, and an initial preventative fungicide is sprayed on all 400,000 acres.

“Timing and coverage are going to be critical,” Padgett said. “Have sprayers calibrated and ready to go, and consider a ground application, if possible.”

Padgett said farmers do not want to be in a position where they have “to play catch up” on crops infected by Asian soybean rust.

“You don’t want to let this get out of hand,” he warned. “If you have two sprays then you want to get the most water out as possible on the first spray if you have to choose.

“A bad application with the best fungicide equals a poor application.”

Lambert offered a checklist of how Brazilian farmers should approach Asian soybean rust:

1. They understand the disease.

2. They find an infection early and get ahead of it via intensive scouting.

3. They know which fungicides and tank mixes proved the optimist efficacy.

4. They are prepared.

5. They make fungicide applications by ground using their own spray equipment.

6. They pay attention to water quality.

7. They get wide spray coverage.

8. They replace used equipment with new one equipment configured to widen soybean row width.

9. They share information with other farmers.

Both men advocate early identification of the disease is axiomatic and farmers and consultants must be diligent in their search for symptoms of infection, which are evidenced by tan-colored lesions.

“There is no substitute for hands-on work for identifying this fungus out in the field,” Lambert said. “Be sure and focus your attention where leaf wetness is going to be the longest each day, maybe on the wet side of a tree line where the dew takes longer to dry off.”

He said the fungus needs a minimum of six hours of leaf wetness to “really get going.”

“Collect leaf samples out of the lower third of the plants and put them in your house or office where the temperature is fairly stable and leave them there for 24 to 48 hours.

“Then take them out and see if you can detect any spoliation on the other side of the leaves.”

Padgett said a common question he is asked concerns carrying the disease from one field into a neighboring one by simply walking across both.

“Maybe, but probably not,” he replied, emphasizing that wind will be the biggest factor in the disease’s emergence.

“These spores are going to move as fast as the wind blows. They are sensitive to ultra-violent light — they don’t all survive,” he said. “But if you have a 10 mile-per-hour wind blowing from the south to the north and you get a spore that can survive, then every 10 hours it is going to move 100 miles. That is potentially 240 miles in a day.”

Padgett said consultants, scientists and growers are all learning about the disease cooperatively.

“It’s a work in progress, we are starting from ground up,” he said.

“There is hope for us,” he added. “We can manage this disease. They manage it in other countries where they are probably going to have a much worse case of it than we will.”

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