Viburnum leaf beetle

Sunday, June 15, 2003

ALBANY, N.Y. -- Wanted: Home gardeners, landscapers, and 4-H groups to help track the spread of a tiny, ravenous beetle that chews flowery shrubs into skeletons. No experience necessary.

To track the rapid migration of the viburnum leaf beetle across the nation, Cornell University scientists are recruiting volunteers to scout back yards, gardens, parks and nature centers for evidence of the pest.

The insect, about the size of a matchstick head, traveled to North America from its native Europe on nursery plants at the turn of the 20th century. Discovered in Canada in 1947, it chewed its way into the United States a half-century later in a New York state park along the Lake Ontario shore. Since then, the beetle has been sighted in parts of northern Vermont, Maine, Ohio and Pennsylvania.

With the aid of volunteers, researchers hope to track the beetle's route; determine how weather and other factors affect its life cycle; discover why some viburnum species are more prone to the insect than others and assess how much damage the beetle causes.

The insect feeds exclusively on viburnum leaves, which gives the foliage a skeletal appearance. Viburnums are a large and varied group of woody plants known for their clusters of fragrant flowers and colorful fruits, which provide food for birds and other wildlife. Reaching up to 20 feet tall, viburnums are often grown for screening or in hedges.

Certain species like the popular arrowwood viburnum are susceptible to the beetle while others like the burkwood viburnum prove resistant. Plants that have been defoliated for consecutive years may die.

Observing bushes

Volunteers participating in the project observe viburnum bushes from late spring to midsummer during the height of the beetle's feeding. Once the insect is spotted, volunteers visit the infested bushes every couple of days to determine exactly when the eggs hatch and note the extent of damage to the leaves.

"We can use all the help we can get," said Lori Bushway, a Cornell senior extension associate in horticulture.

Helen Dolan, a 64-year-old retired professor and avid gardener for more than a decade, recently signed up to inspect five viburnum plants in her West Sand Lake, N.Y., neighborhood, just east of Albany. She'll visit the plants once a week looking for signs of the beetle.

"I figure anything I can do to help and be on the lookout for the beetle, I'll do it," Dolan said.

Volunteers enter observations into the Cornell Web site, where scientists will use the information to pinpoint the spread of the beetle. Cornell maintains online pictures of the beetle and viburnum bush, making it easy for the amateur scientist to identify them.

"Even if you've never heard of this pest before, we can show you how to identify it," Bushway said.

So far, more than 50 people from 20 New York counties and five Pennsylvania counties had registered to search for the beetle. Cornell also has spotters in Ohio, Illinois, Massachusetts and New Hampshire, Bushway said.

In July 1996, E. Richard Hoebeke, assistant curator of the entomology collection at Cornell, encountered the beetle at Fair Haven Beach State Park in Owego, 65 miles south of Syracuse. Before Hoebeke's discovery, the beetle had been absent in the United States. Since then, it had been found devouring plants in 33 counties from far western New York to the Adirondack Mountains.

Adult beetles resemble a small, dark-brown blotch and can be hard to spot. An adult female can lay up to 500 eggs at once and the larvae hatch in late April or early May and feed on the leaves for about a month. Then the adults gorge on the leaves and lay their eggs on the twigs, renewing the cycle.

There are several pesticides that can be used to control the beetle, but most contain poisons that can also kill beneficial insects that help keep the beetles in check. Scientists suggest pruning twigs in the fall or early spring to eliminate the eggs.

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