A serious threat to North American hardwood forests has resurfaced in a big way in Massachusetts, grabbing the attention of forest health managers tasked with protecting Michigan's valuable hardwood stands.

The Asian longhorned beetle (ALB) is an invasive species that poses a serious risk to hardwood trees, including maples, horse chestnut, elms and aspen. The beetle larvae chew tunnels through tree trunks, weakening the tree and making it more susceptible to storm damage and disease. ALB damage also impacts the economy, since the infested hardwood has no value as commercial timber.

ALB was first discovered in Brooklyn in 1996, entering the U.S. in infested wooden pallets and crates. It was discovered in Chicago two years later, followed by finds in New Jersey and Toronto, Canada. ALB has eluded elimination efforts, coming as close to Michigan's borders as Chicago. In early 2008, ALB was thought to be eradicated in Chicago and New Jersey.

"But in the fall of 2008, ALB was found in Massachusetts, indicating we still have a fight on our hands," said Dr. Robert Heyd, Department of Natural Resources forest health management program leader.

The Worcester, Mass., ALB infestation encompasses 62 acres and has led to the destruction of thousands of maple trees.

"This discovery serves as a call for all states to intensify ALB detection efforts," Heyd said. "Our best chance at stopping the ALB is prevention and early detection. In the past, most ALB detections have come from the public. With continued education, Michigan's citizens can help us with both prevention and detection efforts."

A native of China and other areas of the Far East, ALB is a large black insect with white spots on its wing covers. The body of the beetle is one to one-and-a-half inches long with distinctive white and black banded long antennae which resemble horns.

Adult beetles are found in the summer months. Females lay eggs in pits they chew into tree bark. The resulting larvae tunnel just under the bark for a few weeks before boring deep into the tree's heartwood.

The large, showy adults then chew their way out of the tree the next spring or summer. The exit holes left by emerging adults are perfectly round and three-eighths of an inch or larger in diameter.

"ALB attacks the tops of trees first, making detection difficult," said DNR forest health monitoring program leader Roger Mech. "Attacked trees often have yellowing and/or dying branches in the upper canopy. These symptoms may appear before exit holes become visible in lower parts of the tree. Unfortunately, discolored foliage and dying branches also are symptoms of other tree stressors, such as periods of extended drought. This makes detecting ALB difficult, and explains why infestations to date have been found by citizens reporting an unusually large, black beetle with white spots and very long antennae."

ALB attacks many types of deciduous trees, including all species of maple, elm, willow, birch, horse chestnut, London planetree, aspen, ash and mountain ash. Larval tunneling damages the vigor and structural integrity of the tree, and eventually can kill trees or make them vulnerable to storm breakage.

"In Massachusetts, a December 2008 ice storm broke thousands of ALB-weakened trees," Heyd said. "Trees fell throughout the infested area and many residents lost electricity."

It appears that ALB arrived in Massachusetts at least 12-15 years before being detected late last summer. Since ALB was discovered there, about 24,000 trees have been taken down in the city of Worcester as part of the program to eradicate the beetles. Additionally, the U.S. Department of Agriculture will spend $24.5 million in Worcester this year alone for tree removal, surveys and other treatments in the fight against ALB infestation.

These numbers are an indication that ALB not only affects the beauty and health of urban and rural forests, but also has far-reaching economic impacts. Hard maple and aspen alone constitute 27 percent of the forest cover in Michigan, and the two species make up 43 percent of the commercial timber harvested statewide.

If ALB were to become established in Michigan's hardwoods, the estimated economic impacts are in the billions of dollars, Heyd said. The infested trees would not be useable as commercial timber and there also would be impacts on the maple syrup, hardwood veneer, ornamental landscaping and tourism industries.

"The dire outcome of an ALB infestation should serve to motivate everyone in Michigan to keep an eye out for the beetle and to immediately report any sightings of the larva, adult beetle or characteristic signs of damage," Heyd said. "Any possible ALB findings should be reported to the nearest DNR, Department of Agriculture or Michigan State University Extension office."

To assist the DNR in their efforts to keep ALB out of Michigan, DNR forest health, inventory and monitoring unit supervisor Ron Murray encourages campers and other firewood users to buy their wood locally and not transport it from out of state.

"Prevention is going to be the most effective and most affordable medicine against ALB," Murray said. "As awareness of the risks associated with transporting plant material such as firewood grows, the better chance we have of stopping the threat of ALB to Michigan's hardwood forests."

For more information on ALB, go to a U.S. Forest Service Web site: www.na.fs.fed.us/fhp/alb/.