Olive Fruit Fly (Diptera: Tephritidae) in California Table Olives, USA: Invasion, Distribution, and Management Implications

Abstract

Olive fruit fly, Bactrocera oleae (Rossi), was discovered in California in late 1998. Thereafter, intensive research was conducted to develop pest control methods in table olives grown for canned fruit. The life history of olive fruit fly was elucidated, and the distribution and abundance of the adults determined through trapping programs. Olive samples from noncommercial trees were collected from 2002 through 2013 in different locations to determine the maximum number of larvae per fruit. Larvae were most abundant in September and October and ranged from <0.5 to 10 per fruit. The date of maximum fruit infestations may differ annually due to the amount of fruit set, fruit size, and weather. Very high numbers of larvae were collected from large green fruit (≥4 g), whereas smaller fruit (∼2–3 g) supported fewer insects. High larval numbers were found in fruit from areas with cooler summer weather than in fruit from the hot inland valleys. Olive fruit fly larval populations were prevalent in locations with high summer temperatures when buffered by cool marine air flow or slightly higher elevations from the inland valley floor. High larval infestations were found at an arid location with hot summers, suggesting that olive fruit fly may adapt to such conditions. Infested fruit was collected from the same locations in subsequent years, and the proximity of commercial olive orchards may enhance susceptibility to future infestation. Control methods are summarized, including intensive biological control programs and new techniques such as bait stations considered for pest management programs. Basic cultural practices such as removal of nonharvested fruit that support multiple generations, timing of harvest to avoid adult activity, and elimination of standing water required by olive fruit fly adults for survival would be of major importance in reducing pest populations.