Charles Harrington/University Photography

E. Richard Hoebeke, senior extension associate in the entomology department, examines the damage done to foliage by the viburnum leaf beetle.

Two years ago, the viburnum leaf beetle (Pyrrhalta virburni), a pest with an appetite for certain ornamental bushes, was found in upstate New York along the Lake Ontario shore. Since then it has been chewing its way steadily south, and now a Cornell University entomologist says the pest has been found in Geneva, N.Y.

"The damage is very striking. The beetles devour the leaves of the viburnum and totally skeletonize the leaves," says E. Richard Hoebeke, associate curator of the Cornell entomology collection. "There's nothing else that attacks viburnum like that. "

In early June Hoebeke issued an alert to Cornell Cooperative Extension (CCE) agents throughout New York state asking them to be on the lookout for reports from homeowners and nurseries of viburnum damage

"This alert is meant to introduce you to this new pest situation," said Hoebeke in his message. "More importantly, if there are other inquiries from homeowners, landscapers, and arborists coming into the county [CCE] offices, I would like to know about it."

Hoebeke first discovered the viburnum leaf beetle in the area on July 5, 1996, at Fairhaven Beach State Park in northern Cayuga County along the shore of Lake Ontario. That summer he also found the pest in Monroe, Orleans, Niagara and Jefferson counties. Now, two years later, the counties of St. Lawrence, Oswego, Ontario, Wayne, and Genesee have joined the list.

The insect was first discovered in the United States in 1947, although Hoebeke believes the beetle first entered the country from Europe on nursery plants around the turn of the century. It was not seen in North America again until 1955 at Font Hill, Ontario. The insect then went undetected for 31 years, until it was found again in Ottawa, Ontario, and Hull, Quebec. Scientists have kept track of its movement since.

Hoebeke says that the leaf beetle caused severe defoliation of ornamental viburnums in the Ottawa-Hull region in 1978. The beetle attacked the popular European highbush cranberry viburnum or Guelder rose (Viburnum opulus), as well as arrowwood viburnum (V. dentatum complex), American highbush cranberry viburnum (V. trilobum) and mapleleaf viburnum (V. acerifolium).

The beetle is extremely difficult to see, resembling a small dark-brown blotch, about the size of the head of a large, kitchen match-stick. Its effects are unmistakable: Shrubs reduced to leaf veins and branches.

The larvae of the beetle are equally as destructive to ornamental plants as are the adults. Beetle larvae hatch from eggs in early May and feed on the viburnum leaves throughout the larval period, which lasts 8- to 10 weeks. By early to mid-July, the adults begin to appear and continue feeding on what remains of the leaves. They then mate and lay eggs on the shrub's twigs.

Homeowners or landscapers should contact their county CCE office if they suspect the presence of the beetle on their ornamental viburnum tree or bush.

The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) runs an informative web site on the pest. The address is: http://www.gov.on.ca/OMAFRA/english/crops/facts/vlb.htm.