STATE COLLEGE, Pa., Jun 05, 2004 (AP Online via COMTEX) -- Plant experts are predicting a widespread outbreak of wheat scab, a fungus that withers the grain and produces a chemical that can sicken humans and livestock.

Wheat scab, also known as Fusarium head blight, is present every year in small amounts but this year probably will cover crops from the mid-Atlantic to as far west as Missouri or Arkansas, said Erick DeWolf, assistant professor of plant pathology at Penn State University. The disease, a brown film-like covering, is already abundant in Virginia.

"It is pretty bleak," said Don Hershman, extension plant pathologist for the University of Kentucky. "In fact, I just talked with the pathologist at Indiana a little while ago and he said it's bleak there. Illinois isn't good, and Ohio's starting to slide, too."

Scab forms when the Fusarium spores settle in flowering wheat plants. If there's enough moisture and the right temperature conditions - too cold and the spores won't grow, too hot and evaporation steals the moisture - the infection will set in the head as the grain begins to form.

The fungus robs the grain of nutrients, turning the kernels into pale, pruned ghosts of their potential selves. It also produces a chemical called deoxynivalenol, or vomitoxin, that poses a health risk to both people and animals.

"They call it vomitoxin for a reason," said Erik Stromberg, professor and interim head of plant pathology at Virginia Tech.

Stromberg said he's found evidence of infection in almost every field he's seen. Mena Hautau, a Penn State Extension agent, said she saw early signs of scab last week, and expected to find more when she went out Friday.

A multistate outbreak was expected last year because of a wet spring. This year's invasion may take farmers by surprise.

"We actually have had really good growing conditions. The wheat crop was looking excellent, and we didn't have too much moisture," Hershman said. "But it so happened that during the part of the season that it was beginning to flower, there was just enough moisture for the infection to set in."

Some farmers might not even know yet that their crops are infected. The Pennsylvania Agricultural Statistics Service reported Tuesday that as of last week, 76 percent of the state's wheat crop was rated either good or excellent, only 3 percent poor.

But at this time last year, 78 percent of the crop was rated good or excellent. By late July, when farmers were harvesting, that number had dropped to 40 percent, only slightly more than the 39 percent rated poor or very poor.

"Scab has kind of a reputation for doing that. Everything is looking great, and then right before you're ready to harvest all these blight symptoms show up," DeWolf said. "It can be really disappointing."

In Pennsylvania last year, scab was the main reason yields were dropped more than 20 percent, with state's total production falling almost 30 percent to just 7.1 million bushels.

"We figure last year we probably lost 30 bushels per acre because of scab," Schlegel said. "Right now, we could be at about a third of the crop, and it could get worse unless we get into a real favorable position in terms of the weather."

In the nation's top wheat-producing states on the High Plains, there hasn't been enough rain to make scab a serious problem.

Dewolf, the Penn State professor, said past scab outbreaks haven't had a noticeable affect on consumer prices.

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On the Net:

Penn State Wheat Scab site: http://www.wheatscab.psu.edu/

U.S. Wheat and Barley Scab Initiative: http://www.scabusa.org/