NC State Extension Publications

Description and Biology

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The native elm bark beetle, Hylurgopinus rufipes, is a small, brown to dark brown, insect almost 1/8 inch long. The wings and body are rough and have short, stiff, yellow hairs. They overwinter in the outer bark near the base of living elms, and as grubs in the inner bark of dead elms. They breed and construct egg galleries in dead and dying elm trees and even elm firewood. Males as well as females bore entrance tunnels through the bark. Most tunnels have a male near the entrance and a female constructing egg galleries to the left and right of the entrance tunnel between the inner bark and the wood. The egg galleries are formed across the grain of the wood. Minute, pearly white eggs are deposited close together along both sides of the galleries. Young grubs hatch from the eggs and tunnel at right angles to the egg galleries, usually following the wood grain. Once full grown, the white, legless grubs pupate and later emerge as adults. We probably have one generation per year in North Carolina.

Native elm bark beetle

Native elm bark beetles are small and brown.

Native elm bark beetles are rough

Native elm bark beetles are rough and have short setae.

Native elm bark beetle egg ga

Native elm bark beetle egg galleries cross the grain and larval galleries follow the grain.

Host Plants

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Elms seem to be the only hosts for the native elm bark beetle, a vector of Dutch elm disease. American, red or slippery elm, rock elm and cedar elm are very susceptible to Dutch elm disease. Siberian elm is tolerant, but not resistant. These beetles carry the fungal spores of Dutch elm disease on their bodies. When the fungus is introduced into living elms, the water conducting vessels of the sapwood are blocked, killing the trees.

Dutch elm disease

Dutch elm disease first shows up as dying leaves in the canopy.

Dutch elm diseased leaves

Dutch elm diseased leaves turn yellow before falling from the tree.

The Dutch elm disease fungus

The Dutch elm disease fungus plugs up the water carrying vessels of elms.

This is the only real cure for Dutch elm disease.

This is the only real cure for Dutch elm disease.

Residential Recommendations

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Elms should be maintained by proper watering and fertilizing. Native elm bark beetle populations can be reduced by removing and destroying breeding sites such as dead and dying elms and elm firewood. Healthy elm trees should not be pruned between April 1 and August 31, as beetles are strongly attracted to open tree wounds. A pyrethroid insecticide applied to the lower 6 feet of the trunks of living elms during April and May should help protect elms from native elm bark beetles (but not smaller European elm bark beetles!). If elms are specified in a landscape plan, consider planting cultivars resistant to Dutch elm disease.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: Aug. 15, 2017
Revised: Oct. 7, 2019

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