DETROIT - The bloom could be off Michigan's $124-million-per-year blueberry industry after two destructive viruses infected bushes in three locations.

Particularly upsetting to scientists is where one of the outbreaks occurred - Michigan State University's agricultural research station in southwestern Michigan. An outbreak of blueberry shock is forcing scientists to destroy plants that represent two decades and millions of dollars of research.

It will take years for new plants to mature so research can resume, said Annemiek Schilder, an associate professor of plant pathology and a blueberry researcher. Still, she said, "we can't risk having that spread its way through Michigan's blueberry industry."

Blueberry shock is believed to have started in the Pacific Northwest and is spread by bees carrying infected pollen. The virus causes sudden death to flowers and leaves, although new ones can grow.

Plants remain infected but sometimes return to full productivity in a few years.

Blueberry scorch - found on two southwestern Michigan farms - is common on both North American coasts. It is spread by aphids and has symptoms similar to blueberry shock. Some infected bushes die, while others appear normal.

Unlike fungus infections, the viruses have no known treatments.

So far, there is no indication that the diseases have spread beyond those three spots, but the Michigan Department of Agriculture says the risk to the state's 19,000 acres of blueberries remains.

Michigan is the nation's No. 1 producer of blueberries, with 110 million pounds harvested last year. New Jersey was second at 42 million pounds. Nationwide, production totaled 407 million pounds.

Totals for this year are not in yet, but industry groups and growers say Michigan had a bumper crop. Nationally, production is expected to be up as well, according to the North American Blueberry Council.

Blueberry shock spreads only in the spring when bees pollinate bushes' blooms. Between now and then, Michigan State scientists are undertaking a crash study of the disease to learn as much as possible before they have to destroy their plants to prevent the virus from spreading.

Down the road, their work may help commercial growers struggling with infections.

But the losses are great for the researchers working at the Trevor Nichols Research Complex about four miles from Lake Michigan in Saugatuck Township in the midst of southwestern Michigan's blueberry country. The four acres of blueberries there have been used since the early 1990s for research on diseases and pests affecting the fruit.

Schilder's own work at Michigan State dates back 11 years. The university could try to lease land from blueberry farmers to continue its research, but once the station's blueberry bushes are destroyed, no work will be done there for four or five years, she said.

It is unclear how the university's plants got the disease. But Schilder said that if any good came from the outbreaks, it would be in raising growers' awareness of the need to obey a quarantine on untested blueberry plants from Oregon, Washington, British Columbia, and other infected areas.

The Michigan Department of Agriculture is working to track down the sources and any possible spread of the two diseases, said department spokeswoman Jennifer Holton.

"It's like plant health CSI," Holton said. "We're going to figure out how it got into the state and where it spread."