From East to West: The Asian Longhorned Beetle Has Landed

The Asian longhorned beetle has been causing quite a commotion in New York City and Chicago, since its 1996 arrival in the United States. Since then, it has spread around those two cities, leaving weakened trees that must be removed, chipped, and burned to prevent more widespread infestations.

As a result of the invasion, as of December 1998, the United States no longer accepts imports from China, including Hong Kong, packed in untreated wooden packing materials. These materials must be fumigated or treated with heat or preservatives prior to arrival in the U.S. Inspections at ports of entry, by USDA Animal and Plant Health Inspection Service (APHIS) inspectors, have been stepped up. An interim rule has taken effect, requiring treatment of solid wood packing materials to eradicate the beetle and any larvae. Shipments lacking certification of such treatments are subject to APHIS inspection for pest insects or re-export. Importers may be given the opportunity to separate the cargo from the packing materials at a location and in a time frame the inspector specifies. The solid wood packing materials must then be re-exported or destroyed, as directed by the inspector.

The Culprit

The Asian longhorned beetle can be a formidable adversary. As ARS entomologist Michael Smith says, "If its geographic distribution in China is any indication, it has the ability to live and thrive in a wide range of climatic conditions where suitable hosts abound." Indeed, the beetle seems to tolerate the cold winter weather and hot summer temperatures well, all the while feasting on various hardwood trees but especially maples, elms, poplars, willows, ashes and horsechestnuts. "If the relative proportion of trees found infested by the beetle in the United States thus far is an indication of its host preference, as opposed to merely a reflection of the relative species abundance in infested landscapes, it may have a distinct taste for maple trees, which for the eastern U.S. is particularly alarming," warns Smith. Cherry and various fruit trees are also at risk.

In New York and Chicago, street and park ornamental trees such as the Norway maple have taken the brunt of the beetles' invasion. These trees were planted because they show the ability to survive the assault of urban pollution and limited space. But now, the Asian longhorned beetle has compromised their survival.

During the summer months, the adult females lay eggs under the tree bark, leaving a round or oval wound on the trunk and branches. The larvae feed briefly under the bark and then burrow into the center of the tree to feed. When the larvae finally mature to the adult stage, they tunnel their way out of the tree, again leaving a wound in the trunk, this time a 3/8-inch hole. The internal damage sustained by the tree renders it vulnerable to secondary attack by other insects or diseases.

Economic Issues

The economic fallout has been significant: management of the beetles' initial 1996 New York infestation cost the state and federal governments more than $4 million. Last year, U.S. Department of Agriculture Secretary Dan Glickman signed a declaration of emergency, transferring $5.5 million in funds to aid in the detection of the Asian longhorned beetle, identification of infested areas, control and prevention of the beetle's spread to noninfested areas, and eradication of the pest.

"The Asian longhorned beetle is a pest that threatens trees in our forests, rural areas, and even urban neighborhoods," Glickman said. "This additional investment will enable us to further expand our priority prevention and control efforts."

The beetle threatens not only urban economies, but agricultural economies as well. The sugar maple, from which maple syrup is derived, is a particular favorite of the Asian longhorned beetle. Maple syrup production in this country generates almost $9 million in revenue each year. This is but a drop in the bucket to the overall loss potential; total annual revenue from all industries that would be affected by a widespread Asian longhorned beetle infestation in New York alone tops $11 billion. If this beetle and other wood-boring pests were to become fully established in the United States, they could damage industries that generate combined annual revenues of $138 billion.

Interventions

Scientists are currently attempting to find workable strategies to control the Asian longhorned beetle infestation. "The beetle spends the vast majority of its life cycle within the tree, specifically within the interior wood," says Smith. "This makes it particularly difficult to kill after the tree is attacked."

APHIS scientists have conducted field trials in China for 2 to 3 years and are now proposing systemic insecticide treatments by various injection methods, either by injection into the soil or injection directly into the lower tree trunk just above the roots of infested trees. Theoretically, the injections facilitate transport of the pesticide's active ingredient from the application site (root zones) to active areas of tree growth, where the adult beetles feed and lay eggs.

However, until such methods of eradication are realized, the only option remaining in infestation areas is to remove the infested trees, put them through a chipper, and burn the chips. This combination of chipping and burning the wood remains the most effective and economical method of destroying the beetle larvae and eggs within the trees. If this pest is to be eradicated, it is clear that U.S. borders must be guarded vigilantly.

The Interim Rule and Methyl Bromide

Under APHIS' interim rule, several treatment methods have been approved: application of preservatives, heat treatment, and fumigation. Methyl bromide is the only approved substance for fumigation of the wood packing materials.

Methyl bromide used to treat quarantine pests such as the Asian longhorned beetle is exempt from the phaseout. However, methyl bromide may become unavailable at some point in the future because the quarantine exemption may be removed or manufacturers may lose interest in producing it for the small quarantine market. To avoid having to rely on only one fumigant, ARS scientists, at the Horticultural Crops Research Laboratory, in Fresno, California, are testing several potential postharvest fumigants as alternatives to methyl bromide. (See the technical report that follows on the sulfuryl fluoride research at Fresno.)

At the moment, only the treatment of solid wood packing materials prior to arrival on U.S. shores—and the program of destroying infested trees—stand in the way of a widespread and economically devastating infestation of the Asian longhorned beetle.

Last Updated: May 4, 2000