Emerald Ash Borer larvae have cryptic habits. They tunnel beneath the bark of ash trees leaving little outward signs other than small D-shaped exit holes. Larger populations cause much damage that leads to decline of the tree. However, once a tree declines to a noticeable state, it is often too late to save the tree. To better manage EAB, it is useful to know where populations are located before trees are severely damaged.
One way to sample for EAB is to collect branches from ash trees and peel away the bark to locate galleries, larvae, pupae or adults. On my trip to Boulder, Colorado, colleagues were demonstrating the bark peel technique. A branch to be sampled is placed in a stand and held in place with a chain. The inspector uses a sharp adze to peel the bark and wood one thin layer at a time. If a gallery is detected, the bark is peeled deeper to determine the direction of the gallery. The galleries are close to the surface, but when a larva is fully developed, it bores a tunnel deeper in the wood as a pupation site. In the case pictured above, many layers of wood had to be peeled to reach the pupation chamber. The chamber in the picture contains an adult EAB. Adults emerge within the chamber, but do not always exit immediately. This adult escaped a mid-May snowstorm by delaying its emergence.
The Emerald Ash Borer project in Boulder has sampled hundreds of trees and will sample hundreds more in an effort to map the population and know where to focus their effort.