The viburnum leaf beetle is eating itself out of house and home in central, western and northern New York state and elsewhere, says Cornell University entomologist E. Richard Hoebeke. After devastating large swaths of native viburnum as well as ornamental species in its larval stage this spring, the adult beetle is about to return for a second helping in July.

"This is the time we've been dreading," says Hoebeke, assistant curator of Cornell's entomology collection. "I just found viburnum leaf beetles for the first time in the Adirondacks. Sooner or later they'll move into the Hudson Valley and Tri-State area. They are eliminating many species of viburnum from our habitat."

Hoebeke's comments come during a lull in the beetle's destructive life cycle. After a massive outbreak in late April and May, the pest has gone underground to pupate. In the meantime, many viburnum plants, defoliated by the beetle's larvae in spring, have put out a second flush of leaves. When the fully mature beetle emerges in early July, it will finish the job it started.

Hoebeke has been tracking the beetle since its first public appearance in New York on July 5, 1995, at Fair Haven Beach State Park in northern Cayuga County. It is now established in 35 counties throughout the central, western and northern regions of New York. In 2003, the beetle was discovered in Albany and Rensselaer counties, where its origins were traced to infested nursery stock. It also has been identified in seven states, including New York, Maine, Vermont, New Hampshire, Pennsylvania, Massachusetts and northeastern Ohio.

The prognosis is grim: A good portion of New York's native viburnums are threatened with "virtual extinction," Hoebeke says. Many ornamental viburnums, long a landscaper's favorite, are in big trouble as well.

A susceptible viburnum can survive up to three years of double-whammy defoliation, but after that, the bush is most likely doomed, says Paul Weston, Cornell senior research associate in entomology. "It really puts the kibosh on the root reserves and the viburnum can't generate enough nutrients to keep the plant alive," Weston says.

For now, there is no silver bullet. The viburnum leaf beetle is an exotic European species with no natural enemies in North America. The only defense for home gardeners is diligent autumn pruning, and-or applications of expensive insecticides. Biopesticide trials are in place at Cornell's Turf Farm, Weston says. But the speed and intensity of the infestation has so far outstripped researchers' efforts to stop it. In Europe, the beetle's natural enemy is a small predaceous wasp, but importing the wasp poses potential ecological hazards. Other biocontrols, such as microbial or viral pathogens specific to the viburnum leaf beetle, are being investigated. A quick fix is nowhere in sight.

Public education is key to containing the infestation, says Weston, who, along with staff at Cornell's Cooperative Extension, created the Viburnum Leaf Beetle Citizen-Scientist Project, a one-stop info-shop and outreach effort. The project's Web site, http://www.hort.cornell.edu/VLB, provides detailed images of the beetle and of the bush it loves to death. The site also includes extensive information on the life cycle of the beetle, updated sightings and tips on how to control it, among other information. Citizen-scientists can register at the site and use online forms to report sightings and other observations.

The economic impact of the viburnum leaf beetle on the ornamental agriculture business is unknown, but the infestation verges on an ecological disaster, Hoebeke says. The fruit of the viburnum, such as the cranberry bush (Viburnum opulus ), is an important food source for birds. Viburnum also plays an important role in woodland ecology, providing a niche in the under-story where mammals forage and birds nest. Arrowwood viburnum (Viburnum dentatum ), a common field and woodland bush, has been especially hard hit by the voracious pest.

Adult viburnum leaf beetles (Pyrrhalta viburni ) are hard to see, resembling small, dark-brown blotches about the size of the head of a large matchstick.

Young larvae are an off-white color, and in the second larval stage they develop black, uniform spots on their backs. Both larvae and adults are devastating to plants. An adult female can lay up to 500 eggs, and the larvae hatch in late April or early May. They feed on the viburnum leaves throughout the larval period, which lasts four to five weeks. After a subterranean stint, they reappear as adults, usually in mid-July, and consume the second growth leaves. They then mate and lay eggs on the shrub's twigs.

As goes the bush so goes the beetle, Hoebeke says.

"Once the food is gone, their numbers will crash," he says. "But as long as there's a reservoir of viburnum, the beetle will be around. Without bio-controls, it won't end until the last plant is destroyed."