Submitted to: Fruit Flies of Economic Importance International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2010
Publication Date: 9/26/2010
Citation: Yokoyama, V.Y. 2010. Pest, Parasitoid, and Fruit Interactions in Biological Control of Olive Fruit Fly in California. Fruit Flies of Economic Importance International Symposium, September 26 - October 1, 2010, Valencia, Spain.
Interpretive Summary: Olive fruit fly has become a key pest in olives since it was first discovered in California in 1998. Biological control is an economical alternative for costly bait sprays to control the pest in commercial orchards of olives used for canning and oil. An imported parasitoid was released for several years in different regions of the state resulting in successful parasitism of olive fruit fly during the growing season. However, the parasitoid has not yet become established even though adults are long-lived and capable of surviving during the winter. Availability of olive fruit fly larvae in olive fruit was necessary for the development of multiple parasitoid generations; but, the amount of infested fruit in olive trees was limited by high numbers of the pest and inclement weather which caused the fruit to drop. Results suggest that potential future establishment of the parasitoid is limited, but augmented releases may successfully reduce annual numbers of the pest in olives. The research helps protect the California olive industry valued at $90 million annually.
Technical Abstract: Olive fruit fly, Bactrocera oleae (Rossi), and the imported parasitoid, P. humilis, required cool temperatures, high humidities, and food and water for prolonged survival (about 6 months for host) in laboratory and greenhouse tests. Life span was greatly shortened by high temperatures, low humidities, and the absence of food and water. The observations were consistent with high populations of the pest found in cool coastal areas and low numbers that occur in dry, arid inland valleys. The parasitoid was effective for biological control (less than or equal to 100% parasitism) when fruit infestations were high such as in coastal olive growing areas. Non-establishment of the parasitoid was related to the lack of infested olive fruit remaining in the trees during winter. The major factors that caused infested fruit suitable for development of P. humilis to drop from trees were high larval infestations and occasional freezing winter conditions. The parasitoid could survive (about 4 months at 15 degrees C) and reproduce (10 degrees C) in the host during winter. Olive fruit fly larvae were found to complete development in immature fruit 1 cm long increasing availability of host between annual crops.