The olive fruit fly originated in the Mediterranean and parts of Africa. It was first found in the US in Los Angeles, CA in 1998. Since then, olive fruit flies are found in almost every part of California. It is believed that the population that invaded the US most likely originated from shipments from France. Olive fruit flies are considered a major pest of olive crops worldwide.
A typical adult olive fruit fly measures 3/16 of an inch long. They are reddish brown in color with large red eyes. The abdomen is brown with darker areas alongside each segment. As with many species of fruit fly, olive fruit flies can be distinguished by their wings. They have clear wings with a dark spot located near the tip.
Olive fruit flies can complete three to five generations per session depending on conditions. Adults are capable of surviving six months during protected, mild winters.
An increase in fruit flies is generally seen in March or April, mid summer, and in September or October. In cooler coastal climates, olive fruit flies can breed year round. March and April female olive fruit flies lay their eggs in last years fruit still on the tree or wait until the new olive crop is large enough.
In ideal conditions, olive fruit flies can compete an entire generation, from egg to adulthood in 35 days. One female olive fruit fly can lay as many as 400 eggs during her lifetime, usually one egg per olive. A female will deposit her eggs beneath the skin of an olive and the eggs will hatch within two to three days. The resulting larvae undergo 3 separate growth phases and will feed on the fruit of the olive during this time. After about 20 days, the larvae pupate either within the fruit during early to mid summer or will exit the olive and fall to the ground to pupate later in the season. In eight to ten days in the early part of the year, the adult olive fruit fly will emerge to feed. In later seasons or in not ideal condition, the olive fruit fly will remain as pupa for several months.
Olive fruit flies only reproduce in olives, but adults will eat honeydew, pollen, yeast, bacteria, and bird feces found in its environment. California produces over 99% of the olives grown in the US. Care should be taken by the homeowner to monitor any ornamental olive plants on their property.