Native to the Mediterranean area, the olive fruit fly is recognized as the most serious pest of commercial olives. It is capable of infesting up to 100 percent of the fruit on a tree and rendering the harvest unsuitable for commercial marketing or household consumption. The larvae feed on the interior flesh of the olive and introduce decaying bacteria and fungi that cause further deterioration. Infested fruit to be processed as table olives can have a mushy consistency and must be rejected, while olives harvested for oil production will record higher acidity levels, significantly lowering the quality.
First discovered in California in 1998, olive fruit fly is now firmly established in all olive growing regions in the state. A few flies were initially detected in several locations in Napa County during the summer of 2001, but the population rapidly expanded throughout the county during subsequent seasons. Olive fruit fly seems to thrive in our land of temperate climate and abundant hosts – in such settings as agricultural orchards, ornamental landscapes, and abandoned fields.
In Europe and Africa, areas with established natural predators and less restrictive pesticide use regulations, growers have been fighting for decades – with mixed results – to control olive fruit fly. With little hope for complete eradication of this pest, our growers must now think in terms of managing olive fruit fly populations to minimize the potentially devastating impact on the business. Homeowners can also benefit from the research and experience developed over the last few years by the commercial industry.
Management tools for the control of olive fruit fly include several types of manufactured and homemade traps as well as a couple of effective, organically-approved sprays. For up-to-date information on what approach would be most suitable for your activity, please contact the Agricultural Commissioner’s Office.