One of the great things about being in the lumber business is that customers keep you on your toes with their questions. Recently at the Sunapee Craft Fair a turner showed me a beautiful bowl that had some pinholes in it with accompanying attractive "stain patterns" around each hole. A friend had told him the wood was "Ambrosia Maple" and the turner wanted to know if this were correct. I answered that I had never heard of such a specie but that I thought the bowl was indeed Maple and that I had also heard of an Ambrosia Beetle. Maybe the stained holes were from this beetle and that's why his friend called it "Ambrosia Maple"…..Sometimes you guess right.
The Ambrosia Beetle causes pinholes 1/100 - 1/4" in diameter and attacks only recently killed/cut trees, logs, and green lumber. They usually bore into the sapwood of both hard and softwoods although sometimes they affect the heartwood. Interestingly, the beetle does not consume the wood; rather, when he excavates his "tunnel", he introduces two types of fungus.
The first grows on the walls of the "tunnel" and it is this fungus which is consumed by the beetle for nourishment. The fungus is called Ambrosia and the name was passed on to include the beetle.
The second fungus is a staining fungus which, if introduced, causes greenish-gray or bluish-black staining around the pinholes. Unless there are zillions of holes, the strength of the wood is not affected. The beetle loves Oak so much that a "sound wormy" grade has been created.
The damage can be avoided or reduced by converting to lumber and drying ASAP. Of course, there are also some chemicals out there which could be used. If you wanted to store logs, a mill pond would be fine. However, if the log is not totally submerged, any exposed area is fair game to the critter.