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CUES: Center for Urban Ecology and Sustainability

Diagnosis Case: Elm

The differences in characteristics of the different beetles can aid in the proper diagnosis of an elm beetle. The adult Elm Leaf Beetles are 5-7 mm long compared to the European Bark Beetle which is 2-3 mm long and the Native Elm Bark Beetle which is 2-3.5mm. Other diagnostic features such as coloring and larvae will help to distinguish between elm beetles.
Notice in the pictures below that the adult Elm Leaf Beetle are yellowish to dull green, with a black stripe on the edges of each wing cover. There are three dark dots behind the head. The European Bark Beetle has a black head and thorax and reddish-brown elytra. Native Elm Bark Beetles are smaller, dark brown to black in color with a thin covering of short yellow hairs. In addition to learning the differences in characteristics, studying the life cycles can aid in understanding the insects and in identification.

Adult Beetles are in the following order from left to right.
(1) Elm Leaf Beetle (2) European Elm Bark Beetle (3) Native Elm Bark Beetle. Bark beetle photos by John Davidson.

Larvae of the Elm Leaf Beetle are about 12mm long at maturity. They are yellowish in color with two lines of black dots along the back. European Elm Bark Beetle larvae are white, C-shaped and legless, with a brown head. The larvae of the Native Elm Beetle are white and grub-like with pale, yellowish-brown heads.
Part of determining which insect causes the damage is knowing when they are most abundant during the season.
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Type of Insects No. of Generations Insect Stage Time they are present
Elm Leaf Beetle 2 Larvae emerge in mid-June

Adults May - early June
Native Elm Bark Beetle 1 Larvae April - May

Adults June - Summer (present in galleries)
European Elm Bark Beetle 1 Larvae late June and July (present in galleries)

Adult female spring - early summer


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Last modified on March 06, 2013