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The Beetle Battle

How early, aggressive action against the citrus longhorned beetle, cousin of the destructive Asian longhorned beetle, may have thwarted an ecological disaster



WSDA
Basking in the sun on a juniper bush on a warm August day in 2001, the handsome inch-long insect was a glossy black dotted with yellow speckles. Its long antennae made two graceful arcs, rather like old TV rabbit ears. "I knew the moment I saw it that this was very, very bad," reflects John Muth. "The temptation was to squish it."

Fortunately, he put the beetle in jar and took it to the U.S. Department of Agriculture. As it turned out, Muth, the owner of Bonsai Northwest in Tukwila, Washington, was the unwitting recipient of the first citrus longhorned beetles (Anoplophora chinensis) to be introduced into the U.S. The insects had hitched a ride among 369 bonsai maple trees that Muth had imported from Korea, even though he had adhered to all U.S. import requirements.

A cousin of the tenacious Asian longhorned beetle--which since its initial discovery in 1996 in New York City has caused tens of millions of dollars in damage annually--the citrus longhorned beetle offers a case study in how aggressive, timely action can prevent exotic pests from causing large-scale mayhem in local ecosystems. The battle to stop this beetle also demonstrates the difficulties inherent in such an endeavor. It involved the destruction of otherwise healthy trees in homeowners' yards, and required the suspension of normal environmental regulations so that a rapid response could be mounted.

Exotic pests such as the longhorned beetle are a growing problem--an unintended side effect of human travel and commerce. Stowaway insects, fungus or other pests can travel vast distances to ecosystems that are unequipped to combat them. To cite just one infamous example, in the early 1900s the fungus and its beetle vector that are responsible for Dutch elm disease cruised across the Atlantic hidden inside European elm logs shipped to the U.S. They soon decimated the beloved American elm. Modern aircraft--which bring plant materials and other goods from thousands of miles away to any location in the world within hours--have only exacerbated the problem.

Despite stringent regulations, federal inspections and lengthy quarantines, the pests can still escape and wreak havoc. A 1999 study by Cornell University estimated that 50,000 plants and animal species have been introduced into the U.S. since the time of Columbus--with the overall cost in damage and control efforts estimated at $137 billion annually.

Destructive Pests

High on the list of most damaging introduced species are longhorned beetles. Like modern-day Trojan horses, the larvae from China, Korea or Japan may be hidden deep in wooden shipping pallets or in the trunks of trees. Beetles then emerge by creating a quarter-inch-diameter exit hole. Their lengthy antenna can stretch three inches beyond their inch-long bodies. Adults can fly up to several hundred yards to find a suitable host tree, and have been known to reach the rooftop gardens of 18-story buildings. Even in their native China, the Asian longhorned beetles have successfully moved from their original range in eastern China to northern provinces, where they have destroyed 80 million trees.

The citrus longhorned beetle potentially represents a greater threat than its more famous cousin¿the citrus is known to attack 40 additional species of trees and shrubs. Included among the known tree hosts are citrus species, fruit trees such apple and pear, and hardwood trees such as maple, poplar, elm, oak and willow. If that weren't bad enough, "citrus longhorned beetles could probably survive anywhere in the U.S. except Alaska," adds Robert Haack, USDA Forest Service research entomologist.

State Prepared

With this background in mind, Chad Phillips, a Washington State Department of Agriculture (WSDA) project entomologist, received the alarming news by phone. The response was swift. "Everyone grouped together for a few seconds, then we stuffed a bunch of people, nets and equipment in a truck," recalls Phillips. They arrived on Muth¿s doorstep in an hour.

The rapid response by the state was largely made possible by preparations that had been in place for several years. State surveys for Asian longhorned beetles had begun in 1996 at large container ports and pallet-recycling centers following the initial discovery of beetles in New York, and state entomologists had received training from the New York program So when the call came, they were ready to react.

A second beetle at the Tukwila nursery soon announced its presence after the WSDA team arrived, landing on the head of one of the state inspectors. Entomologists eventually captured a third beetle that day, but a fourth outmaneuvered the entomologist¿s nets and escaped into a nearby greenbelt, or wooded area.

The next day WSDA scientists carefully inspected Muth¿s maple trees and found a total of nine exit holes. From this evidence, they concluded that there were up to five beetles at large in the nearby suburban area--an area heavily populated with potential host trees. The final piece in the puzzle was put into place a few weeks later when dissection of the captured beetles showed that one was a fertilized female capable of laying eggs. This discovery established that the beetles had emerged from the trees long enough to both feed and mate, and therefore posed an infestation threat.

If the beetles could arrive in one shipment, USDA officials realized, they could also be in others. They expanded their detective work, quickly reviewing recent import records and suggesting state inspections of additional nurseries.

As a result, a week after the Tukwila beetles were discovered, state entomologists found a second introduction site at a nursery near Olympia, Wash. The seven bonsai maple trees involved had come from a completely separate shipment from Korea. Luckily, only two beetles were thought to have emerged, based on the exit holes found. One beetle had been caught by nursery personnel a few days before the state¿s inspection, and was later determined to be a female. Since these beetles mate only after emerging from the tree, the remaining insect at large, whether male or female, did not pose a reproductive threat.

Preempting Infestation

Like a tiny rock that generates expanding ripples in a pond, the beetle release in Tukwila required a growing circle of response. "We spent a lot of time and effort looking at the logistics of a quarantine, sizes, and what kinds of things should be involved," explains Clinton Campbell, WSDA pest program manager.

The WSDA convened a Science Advisory Panel of local and national experts on longhorned beetles. The panel recommended aggressive action to stop the beetle from becoming established. In April 2002, the state finalized a plan to create a circular quarantine area a quarter of a mile in diameter around the Tukwila nursery. Potential host trees within an eighth of a mile from the nursery would be cut down and chipped, while trees in the next eighth mile would receive a systemic pesticide injection into the main trunk.

The tree cutting, which took place during July 2002, was both precedent setting and contentious. "For forest insects, this is the only case that I know of where we are taking control steps without knowledge that there is an actual infestation," says Haack, who was also a member of the Science Advisory Panel.

Most property owners reluctantly accepted the control plan, but three who lived across 10 lanes of highway from the nursery filed suit against the state to stop their trees from being cut. They felt it was unlikely that any beetles could have flown across such an imposing concrete and asphalt obstacle. "It was very difficult to convince people we had a problem, because we had nothing we could show them," recalls Brad White, WSDA managing entomologist. The dispute was later resolved in County Superior Court in favor of the state¿s right to destroy the trees.

Complicating matters, entomologists also had to contend with stringent state and city environmental regulations, because the site contained steep slopes and a wetland. To bypass the usual red tape, state officials drafted an emergency proclamation to allow the tree removal without the usual state and local environmental permits. Governor Gary Locke signed the proclamation in June 2002, just prior to the beginning of tree felling. The control program to date has cost approximately $1 million.

Next Steps

Ironically, if no new beetles are found, officials will never know whether the aggressive control efforts or simply luck was responsible. "The only way we will ever be proven right is when we find out that we didn¿t do enough," says entomologist Phillips wryly. State entomologists will continue to survey the quarantined area yearly for citrus longhorned beetles for five more years, until 2007, before declaring success.

Officials hope to block future introductions. On August 16, 2002, new federal regulations were introduced that require imported bonsai trees to be quarantined in the country of origin in a fully enclosed greenhouse or screen house for two years prior to shipment to the U.S.

Ultimately, John Muth lost more than $100,000 in trees and retail business. But he is at peace with his decision. "I am very glad they cut," he says. Entomologists, for their part, are grateful. "He did what I would pray every good citizen would do," says Phillips.


James A. Grob is a biologist and freelance science writer based in the Seattle area.
USDA APHIS University of Vermont Entomology Research Laboratory
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