Get Along, Little Longhorn: Riding Herd on a Troublesome Tree-Eating Beetle
An Asian beetle is damaging trees in New York City and Chicago
Ingram Carner was mad. Someone--or something--was drilling holes in the branches and trunks of the 20 Norway maples in front of his property in Brooklyn, New York. As a landlord, he had to protect the trees. So in early August 1996, Carner, then 76, decided to do a stakeout. He set up a folding chair in a nearby parking lot where he could watch the trees without being seen.
He hoped to catch malicious teenagers or woodpeckers in the act. But the stakeout was a bust. "I sat there till about noon--and not a thing," he recalls. That´s when he got up to take a closer look.
He was in for a surprise. Out of one of the holes crawled a black beetle the size of a large thumb. "The horns, the horns!" he remembers, bending down and bringing his hands to his head to imitate a bull. The hornlike antennae of the beetle extended more than an inch beyond its body. Small white spots on its back made the beetle look as though it was sprinkled with sawdust.
Carner had unwittingly stumbled on a wood-boring beetle with a voracious appetite for deciduous trees such as maples. First identified in the United States after Carner´s discovery, this pest today threatens trees not only in Brooklyn but throughout New York City and in Chicago as well.
The wood-boring beetle is a recent example of one of the country´s leading environmental problems: alien species. Some foreign plants, animals and microbes shipped intentionally or unintentionally to this country are destroying or crowding out native creatures. The beetle has joined the ranks of the zebra mussel, the gypsy moth, kudzu and hundreds of other infamous exotics in the United States. These alien invaders are costing the country an estimated $123 billion annually and posing a major threat to imperiled native species, according to a recent study by ecologists at Cornell University.
"The ecological and economic damage caused by invasive species is second only to habitat loss," says Doug Jensen, exotic species information center coordinator with the University of Minnesota Sea Grant program.
Potentially damaging invasive species are rarely spotted immediately. Such was the case with Carner´s beetle, which baffled the local parks department. But city officials wisely sent it to Cornell University, where entomologist Richard Hoebeke identified it as an Asian longhorn beetle. Although the creature is not a problem in the natural forests of its native China, the beetle has become a pest elsewhere in Asia in trees planted as windbreaks and in plantations of poplar or willow trees often used to make shipping crates.
A female longhorn beetle typically deposits from 30 to 80 eggs under the bark of a tree. The larvae burrow into the tree, feeding on the wood as they go. After metamorphosing into adults, the beetles tunnel out in the spring and summer to reproduce. Individual trees are often attacked repeatedly, with successive generations of beetles eating their way through the wood until the tree dies. Carner´s trees, planted in 1983, were slowly being eaten away from the inside out.
Some experts believe the invasion of the Asian longhorn beetle occurred sometime around 1986 after the creatures hitchhiked in untreated wooden crates from China that carried tools for a water treatment facility in Greenpoint, Brooklyn. To date, warehouses in 14 states have found signs of the beetle. As a result, imports of untreated wood from China have been banned. Crates are often reused, however, so infected wood can still spread to other areas.
Indeed, in 1998, Barry Albach, a Chicago resident, found the beetle crawling across firewood in the back of his pickup truck. After searching the Internet to identify the creature, he notified authorities of the second Asian longhorn beetle invasion to hit America. Chicago shipping records indicate the invasion is independent from the one in New York, but scientists would like to confirm this using DNA tests.
So far the beetle outbreaks have been confined to New York and Chicago. Authorities in these cities are scouring infested areas, battling to keep the beetle in check. The greatest fear in New York City is the threat to Central Park, where 26,000 trees are being checked branch by branch. Infested trees are cut down, chipped and then incinerated. In the last three years more than 3,800 trees in New York have met their untimely death this way, and more have been marked for destruction. In Chicago, more than 1,000 trees have fallen.
In the meantime, scientists are looking into other methods to control the longhorn menace. Michael T. Smith of the U.S. Department of Agriculture´s research lab in Newark, Delaware, is working with Chinese scientists to find natural enemies of the beetle in its different life stages. He has learned that the beetle is vulnerable to wasps when it is still a grub living under the bark of the tree, where pesticides have difficulty reaching.
Stephen Teale of the State University of New York College of Environmental Science and Forestry in Syracuse is investigating beetle pheromones, or attractant chemicals. By methodically eliminating the chemicals that don´t work, Teale hopes to discover some that may ultimately catch stragglers or even draw beetles out of hidden infestation areas.
Doug Jensen is hopeful that this research will help scientists curb not only the Asian longhorn beetle, but future invasive species as well. "Unfortunately, the Asian longhorn beetle is just the tip of the iceberg when it comes to invasive species," he says. "I believe that we will never be able to completely close the door, but hopefully with immediate and appropriate actions we can prevent some and mitigate the impacts of others."
Christina Reed reported this article while living in New York City, but she recently moved to Northen Virginia.