Wind spreads disease faster than thought

CORVALLIS, Ore. (Map, News) - Plant and human diseases that travel with the wind can spread more quickly than previously believed, according to a study at Oregon State University and elsewhere. The findings cause concern not only for some human diseases but also a new fungus that threatens global wheat production.

The research concludes that invading diseases do not always progress in an orderly, constant rate and that some airborne pathogens can actually accelerate as they move.

"It's now becoming clear that some types of diseases can spread more rapidly and widely than we anticipated," said Chris Mundt, a professor of plant pathology at OSU. "This makes it especially important, in some cases, to stop a spreading disease quickly if you hope to stop it at all."

The studies explain, in part, how West Nile Virus spread so rapidly across the United States when experts had been expecting a slower movement.They help analyze the progression of some historic disease problems, such as the potato blight that led to the Irish potato famine of the mid-1840s. And they suggest that a new fungal wheat pathogen that emerged a few years ago in Uganda may be a bigger threat to world production than first thought.

Mundt, an international expert on pathogens of several important food crops, has studied wheat stem rust for years.

"If we didn't have crops that could resist wheat stem rust, we pretty much wouldn't have a wheat industry," Mundt said. "From this pathogen we've learned a lot about plant disease resistance in general.

"And this new study confirms that it is crucial to get prepared for the rapid spread of a new variety of wheat stem rust that appeared in Uganda in 1999."

The new wheat stem rust, Mundt said, could attack 75 percent of the world's known wheat varieties, and in a bad year might cause up to 50 percent crop losses in some areas.

"We don't want to suggest that the sky is falling, but major losses could occur if the right set of conditions converges," Mundt said. "This is something that we shouldn't take a chance on. It's already spread to Iran, and the new research shows that its global spread may be about to pick up speed."

He said there is little time to waste. "This wheat disease problem could be global within a few years," Mundt said. "We would be foolish to ignore it."

Most plant and animal diseases spread by contact or proximity tend to move in a fairly predictable way, researchers say. But some carried by wind-carried spores or migrating birds can spread rapidly.

From 2004-06 the avian bird flu spread across parts of Africa, Europe and Asia through migrating birds. From New York City in 1999, the West Nile Virus spread across most of North America within three years.

"It was surprising to see how closely the spread of very different plant, animal and human diseases followed the same mathematical relationship," Mundt said. "This is giving us a better ability to predict how various types of diseases may move, and hopefully prepare for them."

The study was published recently in The American Naturalist, a professional journal.