Answer: What you describe sounds like the olive fruit fly. Although not established in many California olive-growing areas, olive fruit fly poses an extremely serious threat to the California olive industry. A native of the Mediterranean area, olive fruit fly is considered the most damaging pest of olives in southern Europe, North Africa, and the Middle East. The olive fruit fly was first observed in North America infesting olive fruits on landscape trees in Los Angeles County, in October 1998. Detection surveys through May 2000 showed olive fly generally infesting coastal areas from San Luis Obispo south to San Diego and into Baja California as far south as San Vicente. There is considerable potential for spread and damage to the commercial California table and olive oil industries of the San Joaquin and Sacramento valleys and coastal growing districts. Olives grown by homeowners for home curing or oil are equally at risk. Once established, multiple insecticide applications are likely to be required to prevent extensive fruit damage by olive fly.
If you find fruits suspected of being infested with olive fruit fly, contact your local University of California Cooperative Extension office (619) 694-2845). They can help with insect collection and positive identification. Bring samples of infested fruits and make careful notes of the location of the trees.
The worms in question will not affect the leaves of your trees or other vegetation in the yard, but considering the risk they pose to other olive trees, it's important that you get a positive identification and learn the most current control strategies.
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