Dutch Elm Disease: Signs of beetle activity

Beetle emergence holes, the size of the diameter of a pencil lead, and/or sawdust on the bark, indicate burrowing beetles. The beetles are 3.5 mm in size.

Actual size of beetle

European elm bark beetle

Native elm bark beetle

The characteristic pattern of the breeding galleries on the surface of the wood under the bark can also be used to identify these two beetles.

Actual wood sample of beetle galleries

Upper beetle gallery - with the grain - European Lower beetle gallery - across the grain - Native Upper beetle - European Lower beetle - Native