Wendell, thank you for the note. The Native Elm Bark Beetle and the European Elm Bark Beetle are the culprits. Elm Leaf Beetles feed on leaves and are not responsible for transmitting the fungus. Both Elm Bark Beetles eat live and dead woody tissue, which is key to their ability to deliver the fungus.
When they exit the bark, they leave pin-sized holes. Interestingly, the European bug leaves galleries parallel to the wood grain whereas the Native bug leaves traces perpendicular to the grain of the wood.
Elm Bark Beetles are attracted to stressed, dead or dying elms so that they can best complete their life cycle. They lay eggs under the bark in the galleries where they are exposed to the fungus if it is present. Eggs hatch, critters eat bark and the fungus, which is sticky, gets on them. Then they travel around bringing the goop with them to the next stressed elm.
The innoculated elm tries to save the day by shutting down its main systems in a defense attempt. That shut down actually kills the tree.
When they exit the bark, they leave pin-sized holes. Interestingly, the European bug leaves galleries parallel to the wood grain whereas the Native bug leaves traces perpendicular to the grain of the wood.
Elm Bark Beetles are attracted to stressed, dead or dying elms so that they can best complete their life cycle. They lay eggs under the bark in the galleries where they are exposed to the fungus if it is present. Eggs hatch, critters eat bark and the fungus, which is sticky, gets on them. Then they travel around bringing the goop with them to the next stressed elm.
The innoculated elm tries to save the day by shutting down its main systems in a defense attempt. That shut down actually kills the tree.
