Biological control of olive fruit fly in California – release, establishment and impact of Psyttalia lounsburyi and Psyttalia humilis

Authors: DAANE, KENT - University Of California; WANG, XIN GENG - University Of California; PICKETT, CHARLES - California Department Of Food And Agriculture; BLANCHET, ARNAUD - European Biological Control Laboratory (EBCL); NIETO, DIEGO - Driscoll'S; Hoelmer, Kim; BON, MARIE CLAUDE - European Biological Control Laboratory (EBCL); Smith, Lincoln

Submitted to: International Symposium on Biological Control of Arthropods
Publication Type: Proceedings
Publication Acceptance Date: 6/29/2017
Publication Date: 9/11/2017
Citation: Daane, K.M., Wang, X., Pickett, C.H., Blanchet, A., Nieto, D., Hoelmer, K.A., Bon, M., Smith, L. 2017. Biological control of olive fruit fly in California – release, establishment and impact of Psyttalia lounsburyi and Psyttalia humilis. International Symposium on Biological Control of Arthropods. p. 156-158 http://www.isbca-2017.org/index.php?cat=PROccedings.

Interpretive Summary:

Technical Abstract: The invasive olive fruit fly Bactrocera oleae (Rossi) (Diptera: Tephritidae) likely originated in sub-Saharan Africa, where the wild olive Olea europaea cuspidata L. (Wall. ex G. Don) is found and from which the domesticated olive O. europaea europaea L. was derived. Following the path of olive cultivation, B. oleae has invaded central and northern Africa, the Mediterranean basin, south-central Asia, and recently California and northwestern Mexico. In California, B. oleae has spread to all commercial olive growing regions since first being detected in 1998. The lack of effective biological control agents attacking B. oleae in California led to the initiation of a classical biological control program in 2003. A number of parasitoids from B. oleae collected from wild olives in Kenya, South Africa, Pakistan, or Namibia were imported and evaluated at the University of California, Berkeley. Also evaluated were fruit fly parasitoids of other tephritid flies maintained in colonies in Hawaii. Two parasitoids, P. humilis and P. lounsburyi, have been approved for field release in California. A third species, Psyttalia ponerophaga, is still under quarantine review. We report here on the field release and recovery efforts for P. lounsburyi and P. humilis (Namibian strain) in California that were conducted from 2006 to 2013. Psyttalia lounsburyi and P. humilis were supplied by the USDA-ARS European Biological Control Laboratory (EBCL) in Montferrier, France (2008, 2009, and 2013), the Israel Cohen Institute of Biological Control (ICIBC) in Bet Dagan, Israel (2009–2012), and the USDA-APHIS-PPQ, MOSCAMED Parasitoid Rearing Facility at San Miguel Petapa, Guatemala. At all facilities, parasitoids were reared on Medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), cultured on artificial diet. P. lounsburyi colonies were established with parasitized B. oleae collected from olives in Kenya’s Burguret Forest (2002, 2003, and 2005) and Marmanet forest (2007), and South Africa (2005). The P. humilis colony was established from B. oleae collected in wild olives in Grootfontein and Meteorite, Namibia (2007 and 2008). Parasitoid releases were conducted in five California coastal counties where the summer and winter temperatures are relative mild. Releases were also made in three inland counties where the summer temperatures are relatively warm (Napa) or hot (Butte and Yolo counties). The release sites were either clusters of ornamental trees, organic commercial olive groves, or abandoned olive groves. Typically, the trees were Manzanillo or Mission cultivars, but some sites had a mixture of cultivars. The coastal sites were often heavily infested by B. oleae, making them ideal habitats for field colonization and establishment of introduced parasitoids. Pre- and post-release samples were made at all sites. From 2006 to 2013, we released a total of 40,967 female P. humilis and 24,402 female P. lounsburyi were released at both coastal and inland sites. Across all sample dates and sites, parasitism by P. humilis ranged from 0–25%. Recoveries of P. humilis were made immediately following a release date; however, P. humilis did not appear to successfully overwinter, and the longest period between a release and recovery date was 193 days. Parasitism by P. lounsburyi has ranged from 0-60% per collection. Recoveries of P. lounsburyi were made more than three years after the last release at some sites, and some recoveries of P. lounsburyi have been made more than 50 km from any release site. Many factors could have affected the California establishment of P. humilis and P. lounsburyi. Foremost was the limited number of parasitoids available to release. In California, maintaining large B. oleae colonies throughout the season has been difficult. For this reason, the parasitoids were reared on C. capitata in artificial diet, which precluded mass-rea