A Race to Save the Ash Tree

The American chestnut, barely hanging on.
The American chestnut, barely hanging on. (The Washington Post)
By Adrian Higgins
Thursday, August 30, 2007

Square-shouldered and lithe, Dick Bean moves through the forest as sprightly as a tiger. His prey? A shiny green beetle barely an inch from beady eyes to wing tips.

He is leading me through woods to a cornfield in rural Prince George's County. At a clearing near a pond, he stops to examine a fallen ash tree. Scraping the bark from its trunk, he finds a tiny hole in the wood, behind which is staring out the face of his quarry.

He gets a wood chisel to gain better access to the beetle, and then lifts it with a pair of tweezers. "I'm not going to leave them," he said, extracting it by the head. "This is personal."

Bean, an entomologist, is leading the Maryland Department of Agriculture's efforts in the county to contain the spread of the emerald ash borer, an exotic pest of chillingly destructive powers. Bean knows that he is in a race against time, and the very survival of the iconic ash tree is at stake. If he can stop the spread of the pest, scientists may one day find a parasite that can be used against the borer. If not, the tree may go the way of the storied American chestnut, which has been virtually wiped from the continent.

The two most common ash species in this country -- the white ash and the coarser, smaller but tougher green ash -- range from Nova Scotia to Texas. Together, they have been used to decorate countless gardens and parks. Tolerant of poor soils and flooding, they are one of the most common street trees. There are 360,000 in Baltimore alone, Bean said. The ash tree yields fine lumber -- strong, straight-grained and the stuff of baseball bats.

There are lots of reasons to save the ash, but to do that, Bean must first destroy it.

The Asian pest first surfaced near Detroit in 2002 and since has spread from Michigan to parts of Ohio, Indiana, Illinois and Pennsylvania. It made its way to Prince George's County when a Michigan grower sent infected trees to an unwitting retail nursery in Clinton in 2003. After authorities learned of this dire threat to the East Coast's forests and yards, all the ash trees within half a mile of the nursery were identified and destroyed. A year ago, however, inspectors found fresh infestations within and just outside the original eradication zone, prompting the department to draw a new destruction zone around Clinton and Brandywine that covers more than 21 square miles.

Since then Bean and his 14-member staff and an army of volunteers have scoured stream valleys, hedgerows, parks, golf courses and neighborhoods to identify and cut down ash trees. More than 24,000 have been ground into mulch. The affected property owners "weren't pleased their trees were being taken," Bean said, "but they understood the need." They were given $150 vouchers to replace them.

The team has planted more than 600 young bait trees across the area to lure remaining borers and to test sticky traps with chemicals that draw the flying adult beetles. It is the larvae that do the damage, and on the tree from which Bean extricated the adult, he pointed to a spot on the exposed cambium where a single larva had tunneled through the fall and winter to create a winding scar about 12 inches long and four across in its serpentine meanderings. Just a few strategically placed grubs would girdle and kill a tree.

The bait trees will be harvested and ground up before the insect can pupate and emerge next spring as an adult.

Bean hopes fervently that the borer can be beaten in the quarantined areas. Beyond it, he said, "you can't cut down every ash tree. We would be doing the work of the beetle."

One cannot think of the dire threat to the ash without also thinking of the American chestnut, which hangs on by a thread.

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