A Skirmish to Save Md.'s Ash Trees

Scientists Take On A Little Green Beetle

For years the battle has raged: Man vs. nature, entomologists vs. a tiny iridescent green beetle. And hanging in the balance: the fate of every ash tree in Maryland, all of them lethally vulnerable to the beetle's eating habits.

After five years of struggle, scientists say they're no closer to victory. The only thing they've established is that this little bug is one tough cookie.

The emerald ash borer beetle was discovered in the United States in 2002 in Michigan. Back then, U.S. scientists knew almost nothing about the beetle, an exotic Asian insect. Then they noticed ash trees dying by the thousands. By the time they had sized up the threat, the beetle had spread far and wide through the state's forests and moved quickly into neighboring states.

The situation spread to Maryland in 2003, when a Michigan nursery violated quarantine rules and sent an illegal shipment of ash trees to a Clinton nursery. Dozens of those trees were sent out on landscaping jobs across the state and into Pennsylvania and Virginia. Precious months passed before state inspectors discovered the nursery's infestation in August of that year.

By tracking corporate receipts and contracts, state experts were able to find all but two of the 121 trees shipped out on landscaping jobs, but an unknown number might have been bought by walk-in customers who paid cash.

After talking with their counterparts in other states, Maryland entomologists knew the threat the beetles posed. The insects have killed more than 40 million ash trees in southeastern Michigan.

The borers are small; one could fit on a penny. As larvae, they burrow serpentine-shaped tunnels just beneath an ash tree's bark. The tunnels encircle the trunk, stopping water and nutrition from moving up and down the tree, effectively choking it to death in one to three years.

The insect posed particular dangers in Maryland. Ash is the most common tree in Baltimore, with 6 million ash trees in the city and its surroundings. If the beetle became established, federal agriculture experts estimated losses exceeding $227.5 million in the Baltimore area alone.

Although Michigan officials had discovered their problem much too late, those in Maryland had hope. In Michigan, the beetles had chances to spread farther into neighboring states. In Maryland, officials had a known time and point of origin and could work backward to stop infestation.

Working from scientific estimates that the beetle could fly half a mile each year, the Maryland Department of Agriculture created a half-mile-radius kill zone around the Clinton nursery in 2003 and 2004, pulling up and incinerating all ash trees within the radius.

In their place, state experts planted test trees, imported from Minnesota and known to be clean. The next year, they pulled those trees up and tore into the bark. All were clean.

The plan seemed to have worked until 2006, when the telltale tunnels were found in one of the test trees. A more extensive survey of the area by state workers found the problem had grown larger than they first assumed.