The weevils are considered a pest for many species of oak tree due to the damage they cause to acorns.

[3] The female Curculio occidentis lays small batches of two to four eggs in a developing acorn.

The resulting larvae feed on the kernel and when fully developed, tunnel out of the nut, fall to the ground and dig themselves a small chamber.

[5] Together with larva of the filbertworm moth (Cydia latiferreana), the filbert weevil feeds on the acorns of several species of oak tree.

In British Columbia, up to 66% of acorns from garry oak (Quercus garryana) were infected with these larvae.