By Nancy Allen
Small soybean plots that herald the possible arrival of Asian soybean rust -- a potentially devastating fungal disease -- will be planted in Mercer County in the coming weeks.
The North Central Soybean Research Program, United Soybean Board and several federal agencies have joined forces to create an early-detection system for the disease in key soybean producing states, one of which is Ohio.
Mercer County extension agent Todd Mangen, who recently attended a seminar on soybean rust, said it's not a matter of if the disease will come to Ohio, but a matter of when.
Some 83,500 acres of soybeans were harvested in the county in 2003 and it ranked 17th in soybean income out of Ohio's 88 counties, Ohio Department of Agriculture statistics show.
But Mangen said contrary to what some believe, the disease can be managed effectively with commercial fungicides applied to the plants at the right time. Soybean plants should not be sprayed with fungicide until they are in the reproductive or flowering stage, a precursor to bean formation and production, he said. "It (soybean rust) can defoliate the plants and has the potential to be a very devastating disease, but it can be combated," Mangen said. "The fungicides out there definitely work."
Mangen urges soybean producers to seek out unbiased information from land grant universities that have an agriculture curriculum, such as Ohio State and Purdue,
"A lot of chemical companies are saying spray early, but producers will waste their money because they will have to respray if it comes later," Mangen said. "That is not what we are telling them."
Mangen said the test 50-foot by 50-foot "sentinel" soybean plots will be planted to let local agriculture officials know when the disease is here and thus when to tell producers to begin applying fungicide. Most fungicides are effective for about three weeks, he said. If spores are present, disease symptoms will begin appearing in sentinel plots -- before occurring in acres planted on a more traditional planting schedule.
Mercer County likely will get at least one such plot. Mangen said he plans to start talking with producers soon to find a place(s) where a plot(s) can be planted. Organizers would like them planted the first two weeks of April, so the beans will be at least two weeks ahead of the May beans typically planted by farmers.
"This is so we can let people know if rust is here and then they can begin to set their management guidelines," said Anne Dorrance, soybean extension pathologist at Ohio State University.
Dorrance is among the team heading up the sentinel plot concept and is on the cutting edge soybean rust study.
Dorrance said the fungal disease was first confirmed in the United States in 1994 in Hawaii. Experts believe it first came from somewhere in Asia, though they're not quite sure where, she said.
The most recent introduction of the disease into the United States was confirmed last November in Missouri, Ten- nessee, Arkansas, Louisiana, Mississippi, Alabama, South Carolina, Georgia and Florida, and likely was the result of Hurricane Ivan. Asian soybean rust spores are carried on wind and/or storm fronts from one area to another, Dorrance said. Spores can travel up to 1,000 miles in a day's time. One good thing about Ohio and other states with freezing winters is that the spores die out in the winter.
Brazil, which has used the sentinel plot early detection system, has dealt with soybean rust for about three years. South Africa has had it there for four years and India before that, Dorrance said. Expanded soybean production around the world has created a natural land bridge where the spores can hop across continents they was not able to before, she said.
Dorrance said the most difficult thing for soybean farmers will be covering all their soybean acres in a timely fashion with fungicide once spores are detected.
"The challenge is that our growers have so many acres," she said. "In the north central region we have a lot of acres, so it's going to take them several days, if in fact the spores come."
Dorrance said Asian soybean rust will probably be the most watched plant disease in history. Because it is new in the United States, producers' concerns are heightened, she said.
"The most important thing is, it is manageable," Dorrance said. "All the other countries that had it have been able to manage it. We are the last continent for it to get to."
Dick VanTilburg, a certified crop adviser with Auglaize Farmers Cooperative in St. Marys, traveled to Brazil to study the disease last February. From the time soybeans are infected, a producer has about eight days at the most to apply fungicide. There will still be some production loss when spraying fungicide within the eight days, he said. Fungicide costs anywhere from $10 to $15 an acre.
VanTilburg said agriculture officials recommend producers begin checking soybean plants for rust when they begin to flower. Fields should be checked in 10 different areas twice a week.
"This probably won't happen realistically and a lot of farmers say they are going to spray preventatively," he said.