Ambrosia beetles are members of the weevil subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae), and feed on ambrosia fungi. The beetles excavate tunnels and create galleries in dead trees and cultivate the ambrosia fungal gardens, their main source of food.
Ambrosia beetles are attracted to dead or dying trees. Once they find a suitable tree, they bore into the bark, burrowing down to the sapwood or heartwood before excavating shorter tunnels to either side. Each female deposits between 40 and 50 eggs at the entrance of the shorter galleries, where the larvae are reared.
As eggs are laid over a period of several weeks, both young and old larvae live together in the same gallery. The female tends her young as they develop through May and June, carefully cultivating ambrosia fungus in the galleries for them to eat. The females have special organs for storing and carrying the fungal spores. The ambrosia fungus develops on a mixture of wood fibers and excrement and spreads to the various galleries, staining them dark brown or black. Unless consumed regularly, the fungus may close off the galleries, killing the larvae inside.
Ambrosia beetle damage is not considered when performing a WDO inspection because the damage was done before the wood was processed into timber for our homes. The beetles will not infest wood that has been kiln dried therefore they will not infest wood in our homes even though the tunnels, galleries and the distinctive dark stains left behind by the ambrosia fungus may still be quite evident. No treatment is necessary when evidence of Ambrosia beetles is found inside your home.
Ambrosia beetle attack can be recognized by piles of fine, whitish dust found around the 1/16″ entrance holes or at the base of the tree. In lumber, the fungus darkly stains the galleries and these stains can easily be seen.
Adult beetles are long and thin, usually about 1/4″ long. They are reddish brown in color with sharp spines at the back endAmbrosia beetle evidence of their bodies. Fully-grown larvae and pupae are the same size as the adult beetles but are yellowish white in color.
Ambrosia beetles attack most tree species. The beetles target very weakened, dying trees, green logs, and unseasoned lumber. The beetles will only attack trees and logs with high moisture content.