Olive Fruit Flies

Olive fruit flies (Bactrocerae oleae) are most commonly present in areas near the Mediterranean basin, including the Middle East, Southern Europe, the Canary Islands, many parts of Africa, India, Western Asia and Northwestern Pakistan. The olive fruit fly was also introduced to the United States via Mexico and has spread throughout the state of California.

Female olive fruit flies measure approximately 5 mm in length, with wingspans up to 10 mm. Their wings appear transparent with brown spots. The olive fruit fly’s thorax is black in color with a silver-hued dorsal surface marked by three parallel black stripes. Although the olive fruit fly’s belly is also black in color, it is covered by a mottled, grey sheen. The basal regions are striped with pale, slanting bands. An asymmetrical, parallel bar or blotch of reddish brown appears in the center of the apical segments. The terminal segment is reddish yellow in hue and may be marked with brown.

As indicated by its name, the olive fruit fly lives exclusively within the olive fruit. First generations are most active in March and April. Female olive fruit flies often lay their eggs within fruit attached to trees; however, they will also sometimes use fallen fruit as breeding sites. From June to August, second-generation adults develop and attack fruits that remain in the tree from preceding crop growth.

The number of generations produced each year depends largely on location. In the olive-growing districts of the San Joaquin Valley, at least three generations of olive fruit flies are expected each year. In Southern California and in milder coastal regions, continuous development and breeding is observed.