Text by May R. Berenbaum

Beware the Asian long-horned Beetle: It's big, it's bad, and it may be the most destructive insect immigrant since the gypsy moth.

In July 1998 a friend gave barry Albach a tree limb to use as firewood. Albach, a park specialist with the Skokie Park District, north of Chicago, kept the limb in the back of his truck for a few days-long enough to notice that strange black-and-white beetles had begun clambering over its surface. "Working for the park district, I've seen lots of bugs," he remarked later, "and I knew that was one I'd never seen before. I thought it was extraordinary." An Internet search led him to a site created by the U.S. Department of Agriculture, where vivid images revealed the identity of his uninvited passengers: Asian long-horned beetles, coal-black insects with prominent white spots on their wing covers and almost comically elongated, banded antennae.

 Although new to Albach, these inch-long insects were all too familiar to agricultural scientists, who were well acquainted with their ability to kill trees. Federal and state inspectors were immediately dispatched to the Ravenswood section of Chicago to investigate. They found more than 50 infested trees-Norway maples, silver maples, box elders, elms, and horse chestnuts among them. The area was quarantined to prevent the removal of stumps, roots, branches, logs, green lumber, and even debris greater than half an inch in diameter. More inspectors flooded in. By the beginning of September they had found more than 300 infested trees in Ravenswood. Additional infestations were discovered in DuPage County, 20 miles to the southwest, and near the town of Summit, just west of the city. By October the quarantine encompassed almost 12 square miles of Chicago, one square mile of Summit, and one square mile of DuPage County.

 This was not the first time the Asian long-horned beetle had set foot in the United States. Inspectors identified it in a warehouse in Loudonville, Ohio, way back in 1992, in solid-wood packing materials in a shipment from China. But the first real evidence that the beetles had established themselves as American residents turned up in August 1996, in the Greenpoint section of Brooklyn, New York. An alert homeowner noticed that all the Norway maple trees along the street fronting his property were defaced with almost perfectly circular holes, half an inch in diameter. At first the holes appeared to be the work of drill-wielding vandals (not without precedent in the urban jungle), but the large black-and-white beetles crawling on the damaged trees could not be explained away so easily. A forester from the New York City Department of Parks and Recreation collected specimens and shipped them to Cornell University, where E. Richard Hoebeke, a beetle expert, realized right away that they were nothing he'd ever seen. By comparing them with specimens in the Cornell insect collection, he quickly identified them as Anoplophora glabripennis, the Asian long-horned beetle. Two days later he was in Brooklyn, surveying the damage firsthand. 

The Greenpoint infestation turned out to be only one of many. The next month, inspectors from the Animal and Plant Health Inspection Service discovered an infestation in Amityville, New York, about 30 miles east of Brooklyn. In December a state quarantine was imposed; a federal quarantine followed in March 1997. In April 1998 the beetles were reported in Queens, at the edge of the quarantine line. In September 1998 infested trees were found outside Amityville, in Lindenhurst. The beetle's July appearance in Chicago, 900 miles away, was an unpleasant surprise. Hoebeke and other entomologists agree that this newly introduced species may be the worst urban menace to hit American shores since the gypsy moth arrived more than a century ago. "If it becomes established," says Lawrence Hanks, a long-horned beetle expert at the University of Illinois, "the Asian long-horned beetle could wipe out a quarter of the shade trees now growing in U.S. cities."
 

In its native asia, anoplophora glabripennis is known as the starry-sky beetle because of its dramatic markings. It attacks and kills trees in China and Korea-mostly maples, poplars, and willows but also mulberries, chinaberries, horse chestnuts, birches, and elms. In the United States the beetle's tastes haven't changed much; it attacks a range of species but exhibits a definite preference for maples. The implications are enormous. Maples are the most widely planted shade trees in many northeastern cities. And the maples of New England, which support a $20-million-a-year syrup industry and a tourist industry that depends on fall foliage, are uncomfortably close to the site of the first reported infestation. 

People in other parts of the country shouldn't be complacent, however. The native distribution of a species is often a good indicator of its ability to establish itself in a new locale. The red imported fire ant, for example, is native to South America's Amazon; since it was accidentally introduced to the southern United States 50 years ago, it has failed to make major inroads in states with cold winters. Unfortunately, the Asian long-horned beetle is a major pest in latitudes from 30° north to 43° north-roughly, New Orleans to Milwaukee. In other words, it is well adapted to infest most of the continental United States. 

The modus operandi of the Asian long-horned beetle resembles that of many of its relatives in the family Cerambycidae. After mating in early summer, a female finds a secure spot on a branch and chews a hole in the bark with her strong mandibles. She then turns around and deposits a single white egg, 1/5- to 1/4-inch in length, and covers it with a cementlike substance she secretes from her abdomen, which may serve the dual functions of preventing desiccation and repelling other females. Over the course of her 40- to 60-day lifetime, a female can lay as many as 40 eggs. After a week or two, the egg hatches and the larva gnaws inward, penetrating the inner bark and riddling it with tunnels; a maturing larva may bore several feet. As they burrow, larvae push frass, a mixture of chewed sawdust and excrement, out of the tunnel behind them. Upon reaching their full size (two inches or so), larvae pupate and then overwinter in their tunnels. As adults, they chew out a dime-size exit hole to emerge and begin the cycle again.

 Cutting through sapwood has a major impact on tree health: Sapwood is the tissue through which nutrient-rich fluids travel to the leaves, the energy factories of the tree. Trees with damaged sapwood thus grow weak, and their upper branches wither and die. They may lose limbs in heavy winds. A severe infestation can kill a tree outright, although it may take several years of concerted tunneling by several generations of beetles. Trees that survive may be damaged beyond economic use for lumber or veneer. But even in Asia, where the long-horned beetle is a familiar adversary, few control measures are available. Pesticides are generally ineffective, because the beetles spend such a long time concealed deep within the tree, out of reach of most sprays. Predators and parasites do not appear to have much impact on beetle population growth either. A considerable research effort has nevertheless been launched in hopes of identifying a biological Achilles heel among the six legs of the Asian long-horned beetle. Scientists are investigating its pheromone chemistry, its mating, and its egg-laying behavior in strictly monitored quarantine facilities within the United States; several experts have traveled to China to seek out natural enemies that might knock its numbers down. Evidence from China suggests that beetle damage can be reduced by planting tree varieties that are resistant or unpalatable to the beetles. It is unlikely, however, that an immediate solution will materialize. 

So far, the only viable option for containing infestations seems to be cutting down, chipping, and burning all affected trees. In New York State, some 3,850 trees have been destroyed, more than 80 percent of them maples. The bill for the destruction and replacement with less susceptible species, paid by city, state, and federal governments, was $10 million. In Chicago, the count of trees destroyed is approaching 1,000; in March 1999 the city received $1.4 million in federal emergency funds for the cleanup effort.

How effective this plan of attack will be remains to be seen. Because symptoms may not appear for several years, it is difficult to identify trees that harbor the beetles. Moreover, though long-horned beetles are not exceptionally good fliers as beetles go, they can probably move beyond quarantine boundaries on their own power. 
 

Given the frequency with which a. glabripennis and its close relatives have been found-in more than 30 warehouses in 14 states since 1992-it's remarkable there haven't been more infestations. In June 1997, for example, the California Food and Drug Administration reported finding long-horned beetles crawling out of wood crates containing heavy machinery in an auto-repair shop; infested crates had already been shipped on to eight other states. In September 1998, in response to the Chicago outbreak, Secretary of Agriculture Dan Glickman announced an interim ban on the importation of Chinese goods packed in untreated lumber. U.S. trade with China has increased astronomically in recent years and now exceeds $70 billion annually in imports; the number of insects found in materials imported from China has increased with it, from 1 percent of all interceptions in 1987 to 20 percent in 1996. In many cases, the Chinese use poor-quality lumber for shipping crates; poor-quality often means insect-infested. But as of December all solid-wood packing material from China must be certified free of bark (under which insects may lurk) and heat-treated, fumigated, or treated with preservatives.

 How effective the importation ban will be is an open question. The Asian long-horned beetle is far from the only insect that shows up uninvited. And of the 2,000 species of exotic insects established in the continental United States, at least 400 attack American trees and shrubs (see "Invading Armies," right). The Animal and Plant Health Inspection Service, or APHIS, is charged with protecting U.S. borders from foreign pests. But the odds favor the invaders, by sheer force of numbers. In 1996 some 1,300 APHIS quarantine officers were responsible for inspecting 410,000 planes and 53,000 ships. Unauthorized travelers were intercepted 48,483 times. Tens of thousands more insects most likely entered the United States undetected. 

Fortunately, for most of these insects, getting a foothold in a new environment is difficult. Say what you will about ice storms and blizzards, they protect us from untold biological unpleasantness. Thousands more insect invaders are done in by their own fussiness-tree species or environmental conditions that aren't exactly to their liking. Even more are picked off by hungry woodpeckers, cuckoos, wasps, predaceous beetles, and the rest of the biological army of carnivores that patrols the nation's borders. But every ship that arrives from a foreign port, every plane that arrives from another country, is a potential source of new pests. Ironically, just as humans have created globe-hopping monsters through our international trade practices, we've also created their victims. Problems with wood-boring beetles are most severe in cities because that's where trees experience the greatest amount of stress. They're exposed to smog-laden air, compacted soil, excess heat from asphalt surfaces, and most important, inadequate water supplies to roots constrained by concrete. New species of wood-boring pests can easily tip the balance against survival. 

During the summer of 1999 the Asian long-horned beetle was discovered in Chicago in at least three sites outside the quarantine area. Established populations were also found in three new sites along the New York front, including a small park just four blocks from Central Park. Perhaps indicative of the new respect these unwelcome aliens have gained is the one-minute film segment produced by the U.S. Department of Agriculture and airing in the New York area, advising people to be alert to the encroachments of the Asian long-horned beetle. The segment is narrated by John Walsh-best known for serving the same role in the television series America's Most Wanted. 
 

May R. Berenbaum is a professor of entomology at the University of Illinois. Her latest book is Bugs in the System.
 
 

Invading Armies The Asian long-horned beetle isn't the only insect invader to wreak havoc on American trees. When a new insect appears, however, the outcome isn't always easy to predict. History has seen spectacular disasters as well as near misses. To keep abreast of what's going on, check out http://ceris.purdue.edu/napis/pests. Conquering Hordes Name: European elm bark beetle, Scolytus multistriatus. Description: Dark reddish brown, less than 1/8-inch long, chunky in build, round-shouldered in profile. Date of entry: First reported in Boston in 1904. Means of entry: Probably in a shipment of Carpathian elm logs from Europe. Modus operandi: Tunnels through inner bark of elm and basswood trees; transmits fungus known as Dutch elm disease to host tree. Impact: Elms all but vanished from urban streetscapes. By the 1970s elm populations in 45 of the lower 48 states had been irreversibly damaged, some 77 million trees in all. Status: Clones of two survivors will be commercially available this spring: New Harmony and Valley Forge.  Name: Balsam woolly adelgid, Adelges piceae. Description: Tiny (1/25-inch long), round, blue-black to purple in color, with woolly threadlike filaments. Date of entry: First reported in Brunswick, Maine, in 1908. Means of entry: Brought in from Europe, probably on infested nursery stock. Modus operandi: Uses its piercing/sucking mouthparts to ingest plant sap; injects a deadly toxin that distorts growth and kills the tree. Impact: Responsible for the death of billions of board-feet of fir timber in the eastern United States and Canada and in the Pacific Northwest. Fraser firs in the southern Appalachians almost completely wiped out; rare mosses and liverworts endemic to the Fraser fir may have perished as well. Status: Fir trees elsewhere in the insect's range are still at risk.  Isolated Terrorists? Name: Asian gypsy moth, Lymantria dispar subspecies. Description: Hairy gray caterpillar with white and orange racing stripes. Male is gray-brown, 11/2 inches across; female is white, 3 inches. Date of entry: 1991. Means of entry: Egg masses attached to ships or cargo from eastern Siberia. Modus operandi: Caterpillars chew foliage of more than 600 species of trees. Females can disperse over long distances, allowing them to colonize new territory quickly. The fear: Could cause vastly more damage than its infamous relative, the European gypsy moth, which defoliates 4 million acres of forest a year. Has twice as many potential host plants and much greater dispersal abilities. Status: Foreign vessels and cargoes in U.S. and Canadian ports at risk are inspected for egg masses before docking.  Name: Pine shoot beetle, Tomicus piniperda. Description: Small (1/8- to 1/5-inch), brown, cylindrical. Date of entry: First infestation in New Jersey in 1913; intercepted more than 100 times since 1985. Means of entry: Infests solid-wood packing materials. Modus operandi: Females excavate tunnels inside pine trees and lay eggs; larvae consume tissue under the bark; adults fly to tender young pine shoots and bore into them, creating tunnels up to four inches long and causing shoots to fall off. The fear: Because it favors Scotch pine, a holiday favorite, could destroy the Christmas tree industry. Status: Federal and state agencies have imposed a quarantine in 267 midwestern and eastern counties, requiring the inspection of lumber and nursery stock. -M. R. B.