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
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
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
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