The Filbert weevil (Curculio occidentis) and Filbertworm (Curculio occidentis) are two common pests of oak acorns. The larvae of these insects live and feed in the acorn and can cause significant loses. There are currently no effective methods for control of these pests. Insect damaged acorns may also get secondary bacterial infections that cause drippy oak disease (Erwinia quercina). There are some very good guides available; the UC IPM Guide, the excellent Field Guide to Insects and Diseases of California Oaks, and UC Oak Woodland Management Guidelines.