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.
American chestnuts were one of the predominant species of hardwood in forests east of the Mississippi. The tree played a major role in American history and culture: The wood was excellent for timber, rot-resistant and straight-splitting, and the nuts were a significant source of food for people and wild game. It didn't hurt that with great age, the chestnut formed a beautiful thick and furrowed trunk and a broad spreading canopy.
A century ago, a blight disease arrived from Asia and went to town on a defenseless species. The resulting canker destroys the vascular system. Typically, a tree might fall or be cut down, but new suckers would emerge from the persisting root system. Once the stems grow for a few years, the blight returns to kill them. A fraction of these ghosts turn out to have a genetic resistance to the disease, so while they may get the disease and eventually succumb to it, they can grow as high as 60 or 70 feet, develop a 12-inch-thick trunk and produce fruit.
These survivors are now helping to restore the chestnut through the efforts of the American Chestnut Foundation, whose staff members have raised 17,000 resistant trees on more than 130 acres in southwestern Virginia. Scientists started by crossing blight-resistant Chinese chestnut trees with surviving American ones, and then used those hybrids to produce successive generations of purely American hybrids.
Volunteers with the foundation's fledgling Virginia chapter are now using pollen from that breeding program in making new lines of resistant chestnuts. This is how I found myself on the first Saturday of the summer in a woodland in Fauquier County with volunteers Deborah Fialka of Fairfax, and Jack LaMonica of Marshall and his son John, a recent Virginia Tech grad. Bartlett Tree Experts had donated the services of an impressive cherry picker truck and its operator, Jimmy Bergdorf.
Two weeks earlier, volunteers had prepped one tree in Fairfax, surviving in the midst of a townhouse development near George Mason University, as well as four trees at two locations around Marshall. Using the cherry picker and ladders, they had removed the emerging male catkins of each inflorescence and then covered the immature female flowers in white bags, to prevent uncontrolled pollination.
Fialka, who had spent almost an hour in the air pollinating the Fairfax tree, handed me a vial of pollen and suggested I go aloft with Bergdorf at one of the Marshall sites. With the hydraulic arm fully extended, we found ourselves in a peaceful, leafy world, and the idea that I held the future of the American chestnut in my hands seemed to chase away any thoughts of vertigo.
The team will return in September to harvest the nuts, which will be planted in an orchard at the Virginia State Arboretum east of Winchester and on private land. The chestnuts will take at least seven years to produce another generation of nuts.
At our final site, minus the cherry picker, we held a huge wooden stepladder while Jack LaMonica repeated the process. There was something uplifting about all this, knowing that while those of us in middle age won't see the giants that once graced the forests of Appalachia, John's children or grandchildren might. Or as Fialka put it, "You and I have never tasted a Virginia ham fatted on chestnuts. That would be something."
How easy it is to kill a tree. How hard to bring it back.