The olive fruit fly is a recent, unwelcome addition to the world of olive growers here in the US. It was first recorded in California, in October 1998, when a single female fly was captured in west Los Angeles. Currently, the olive fruit fly occurs in all olive growing areas of California and threatens virtually all commercial and fruit-bearing ornamental olive plantings. Here in Ojai, dealing with the fruit fly has become a regular part of our annual calendar, but is something that can be successfully managed,.
The larvae of the olive fruit fly feed inside the fruit, severely damaging the olive, and allowing the entry of secondary bacteria and fungi that make the fruit rot and degrade the quality of the olive oil. In areas of the world where the olive fruit fly is well established, it has been responsible for crop losses of 100% of some table cultivars and up to 80% of oil value. It is considered the most devastating insect pest of olives in the Mediterranean region, where it has occurred for more than 2,000 years. I guess we’re lucky it’s a fairly recent addition out here, and that folks in Europe have lots of practice in combating the problem. For table olive growers, the presence of even a few infested fruit can lead to rejection of an entire crop. Some infestation can be tolerated in olive fruit used for oil production as long as the fruit are not rotten. When we make olive oil, we only allow 5% fruit damage or less, as we find too much fruit fly will result in a poorer quality oil.
Hanging GF120 bait traps to catch the flies is a big part of our summer. The traps need to be placed in about every other tree, which means thousands of them, and needs to be refreshed every couple of weeks. It’s a somewhat tedious but crucial part of the process. The bait (GF-120 NF Naturalyte Fruit Fly Bait), is an organically acceptable product containing the biologically produced insecticide Spinosad. It attracts olive fruit fly adults, which feed on the bait, and causes adult mortality. If you have olives and want to protect them so that you can either cure the fruit for table olives, or pick and mill them to make olive oil, please reach out to us anytime for advice. We can give you the full breakdown of what to use, how and when to use it, and are happy to meet you at your trees and discuss in person if you like.