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New Wave Of Caterpillars Defoliating Oak Trees

PROVIDENCE - The Rhode Island Department of Environmental Management (DEM) reports that small concentrations of orangestriped oakworm caterpillars have begun defoliating trees in areas of western Rhode Island. The caterpillars feed on the foliage of all species of oak trees and have been detected in forested areas in central Scituate and Coventry and parts of Foster that were previously stressed by gypsy moth and forest tent caterpillars. Other areas in the state may also be affected.

Unlike gypsy moth, orangestriped oakworm is native to North America and can be found throughout New York and New England, and from Wisconsin to Georgia. Although outbreaks of orangestriped oakworm occasionally cause widespread defoliations lasting two to four years, insects, diseases and other natural enemies build up over time and reduce the population to tolerable levels. Pockets of defoliation are typically less than 1,000 acres. In 2005, nearly 16,000 acres were affected in central Scituate and Coventry.

Orangestriped oakworm defoliate trees in late summer/early fall and don't pose a significant harm to trees because the leaves have finished photosynthesizing and are beginning to harden off for winter. "We see some amount of defoliation from this native insect every year. It's not generally a problem because defoliation happens so late in the year, and we normally wouldn't expect to see much additional tree death," said Heather Faubert of the University of Rhode Island Department of Plant Sciences and Entomology.

However, because oak trees have already been stressed this year by drought and defoliation by gypsy moth, measurable tree mortality is expected. If standing dead trees become a safety hazard they should be removed. Homeowners are encouraged to seek the services of a Rhode Island licensed arborist to provide that service. Visit DEM's website for a list of companies that employ (self-reported) a licensed arborist.

Standing dead trees can be beneficial as they provide homes to many cavity-nesting birds and perches for raptors. Forest landowners managing their property for forest uses should consider these and other wildlife values and work with their forester to incorporate these goals into their management plans, and use a DEM-registered Wood's Operator should any removals or salvage operations be needed. For questions, email DEM's Division of Forest Environment at

For additional information on orangestriped oakworm, visit Follow DEM on Twitter (@RhodeIslandDEM) or Facebook at for timely updates.

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  • Department or agency: Department of Environmental Management
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  • Release date: 09-19-2017

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