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Elm Bark Beetle

Elm bark beetle

Elm bark beetle gallery (small)

About Elm Bark Beetle

Lives on elm, especially American, Siberian, and Chinese elms.  These beetles are vectors of the fungus that causes Dutch Elm Disease; they carry fungal spores from diseased to healthy trees.

Larvae are grub-like and white.  Adults are brownish-black, thinly covered with short yellow hairs, and about 3 mm long.

In early summer adults females lay eggs in tunnels mined between the sapwood and bark.  During summer, larvae extend these tunnels in the inner bark.  There are two generations per year in the southern part of their range, but only one in the northern part.

Leaves of diseased branches turn yellow to yellow-brown and die.  After the beetles emerge, the bark of infested branches and trunks is marked by numerous pin-head-size exit holes.  Sawdust-like frass accumulates below infested tree parts in cracks and crevices, or at the bases of trees.

To Control

There is no practical chemical control.  In the spring, kill adult beetles before they mine into high value trees to feed and breed by spraying methoxychlor or chlorpyrifos on the bark.  Thiabendazole injection will arrest the Dutch Elm Disease fungus.  A community-wide sanitation program is advised.  AS soon as an infestation has been diagnosed, infested trees or portions of trees should be removed, debarked, and either burned or buried beneath .5 m of soil.