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.
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Photo: Maryland Department of Agriculture |
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 on landscaping jobs across the state and into Pennsylvania and Virginia. Precious months passed before state inspectors discovered the nursery's infestation in August 2003.
By tracking corporate receipts and contracts, state experts were able to find all but two of the 121 trees sent 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.
Some beetles must have survived, and some must have traveled farther than the half-mile estimate in 2003. By last year, the kill zone had grown to a 25-square-mile area. All told, more than 36,000 ash trees have been cut down and destroyed.
But the beetle has proved to be a tricky and resourceful insect. In recent weeks, the emerald ash borer was discovered for the first time in Charles County, in trees about two miles south of the newly enlarged kill zone.
"It tends to pop up any time we think we have it under control," said Carol Holko, chief of the state Agriculture Department's plant protection section.
The problem is that some beetles, particularly females, can fly farther than the half-mile scientists believe to be their limit. Others hitchhike on people or firewood that campers transport from campsite to campsite (an action now banned in Prince George's and Charles counties). And even though workers have pulled up and destroyed, by burning or chipping, all known infested trees, the beetles can survive in fallen branches or unseen roots.
Their knack for surviving and spreading has allowed them to disperse in recent years to Ohio, Indiana, Illinois, Pennsylvania, West Virginia, Wisconsin and Missouri. This year, the insects were rediscovered in Fairfax County after a five-year hiatus.
For Maryland, the discovery of the beetle along the northern tip of Charles has sparked some minor reevaluation. The infestation of about a dozen trees along Mattawoman Creek is believed to be related to the original outbreak in Clinton and Brandywine.
"There was some fear that the population had been there undetected for many, many years, which would have been really bad," said Dick Bean, field operations supervisor for the state's program that deals with the borer problem. "Now, we think they have been down here two or three years at the most. It hasn't had a chance to become widespread in Charles."
But after years of dealing with the persistent bug, state experts have grown cautious about saying or even thinking anything too optimistic.
Five years ago, when agriculture staff members started dealing with the beetle, they dubbed the program the Emerald Ash Borer Eradication Project.
Now, they mostly refer to it as "the program."
Holko, who is in charge of the project, said, "I'm not ready to say elimination is totally out of the question, but it is becoming increasingly less realistic."
There is also hope on the horizon, however, as knowledge about the insect grows, Holko said. Researchers in Michigan have begun experimenting with importing natural parasites from Asia that prey on the borer beetle. And they have developed sticky traps that emit an alluring smell to catch the beetle.
Some Maryland workers liken their efforts to those of a doctor fighting cancer. Their goal in part is to keep the cancer from spreading, to buy more time for a cure to be discovered.
"This is one tough and tricky insect," said Bean, who has been supervising field operations against the beetle since it emerged in Maryland. "You know, man can take a stance against Mother Nature, but I don't know that he can win. Mother Nature is pretty resilient."