NC State Extension Publications

Description and Biology

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The smaller European elm bark beetle, Scolytus multistriatus, is dark reddish brown, shiny, and about 1/8 inch long. The underside of the rear is concave, with a noticeable projection or spine. Larvae are small, white grubs found under the bark of dying or dead elms. The egg galleries are straight and parallel with the grain of the wood and the larvae feed across the grain in the cambium just under the bark. Larvae develop through the summer months and also overwinter as grubs in “brood” trees. (Brood trees are dying or dead elms usually infected with Dutch elm disease.) Development from egg to adult beetle takes six or seven weeks in warm weather. New beetles fly to healthy elms to feed and then fly to dying or dead elms to breed. They can not breed in healthy trees although they can infect healthy elms with the Dutch elm disease pathogen as they feed. Smaller European elm bark beetles produce an aggregating pheromone, and host plant odors also play an important role in attracting the beetles to susceptible host trees. They have two to three generations per year here in North Carolina. Due to overlapping of generations, adults may be present almost continuously from April to October. The smaller European elm bark beetle is a serious pest of native and introduced elms because it is an important vector of the Dutch elm disease.

Smaller European elm bark beetles and small and dar.

Smaller European elm bark beetles and small and dar.

Smaller European elm bark beetles have a peculiar rear end.

Smaller European elm bark beetles have a peculiar rear end.

Egg galleries (with the grain) and larval galleries (across grai

Egg galleries (with the grain) and larval galleries (across grain) occur in the cambium layer under the bark.

Dutch elm disease typically starts at twig crotches and moves do

Dutch elm disease typically starts at twig crotches and moves downward.

 feed on healthy twigs.

New smaller European elm bark beetles feed on healthy twigs.

Feeding sites may become infected with Dutch elm disease.

Feeding sites may become infected with Dutch elm disease.

Host Plants

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Smaller European elm bark beetles infest all of our native elm trees as well as Siberian elm and Japanese zelkova. Drought stress predisposes exotic elm species to infestation. Dutch elm disease is primarily a problem in American elm.

The Dutch elm disease pathogen

The Dutch elm disease pathogen travels from twigs to trunk to roots.

Residential Recommendations

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It is possible to spray elms with a pyrethroid to prevent further bark beetle infestation. Because smaller European elm bark beetles infect elms by feeding in twig crotches, the whole canopy must be sprayed in spring before bud break and again after the new growth has emerged. Once a tree contracts Dutch elm disease but before the trunk and larger branches are infested, try to control the disease by pruning out dead and dying branches and paint the wounds with tree wound dressing. In urban settings, rapid removal of beetle infested, Dutch-elm-disease-infected American elms followed by destruction of the host material may slow the progress of Dutch elm disease. The wood from infected elms should be destroyed or debarked and the bark destroyed to prevent smaller European elm bark beetles from emerging successfully from such wood for month afterward.

A practical control for Dutch elm disease

A practical control for 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

Extension Entomologist
Entomology

Publication date: March 18, 2014
Revised: Oct. 14, 2019

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