Biological control of olive fruit fly, Bactrocera oleae, in Israel


Abstract: Bactrocera oleae, the olive fruit fly (OFF), is a key pest of olives in most olivegrowingcountries in the Mediterranean basin and elsewhere. It significantly reduces yields anddegrades the quality of the oil extracted from infested fruit. Olive growers have traditionally usedsystemic organophosphate insecticides to control the pest, but it is anticipated that thesepesticides will be banned in the near future. Biological control with imported OFF parasitoidscould help manage fly populations. To increase the production of parasitoids that are entirelymass-reared on Israeli flies, two OFF lines were established on an artificial diet: 1) the wildIsraeli flies “Yael” line (100% “Israeli” genome), and 2) progeny of a laboratory strain importedfrom Crete and crossed with the Israeli wild strain. Four crosses were made and the resultingcolony, the “Argov” line, had a 93.75% “Israeli” genome. Two species of OFF parasitoids wereimported to Israel and maintained in culture: three lines of Psyttalia lounsburyi (originally fromKenya: Burguret forest and Marmanet forest; and from South Africa: Cape Prov.), and Psyttaliasp. nr. concolor (also called P. humilis) (from Namibia). Because it proved difficult to rear thePsyttalia spp. on B. oleae, the cultures were instead maintained on medfly. Field releases of theimported parasitoids started during November 2008 and were continued from June to November2009 and 2010. A total of 37,000 individuals of P. lounsburyi were released on 67 occasions at 22sites, and a total of 97,000 individuals of P. nr. concolor were released on 77 occasions at these22 sites. During 2007, 2008 and 2009 a survey was conducted to document the indigenous andany imported parasitoids attacking OFF in Israel. In 2007 the total parasitism rate in fruit samplesreached 11%. Seven species of parasitoids emerged from olive fruits, dominated by the braconidsP. concolor (local species) and Diachasmimorpha kraussii (previously released against Ceratitiscapitata). All other species belonged to the Chalcidoidea. During 2008, the pooled parasitism ratein fruit samples reached 15%, including 63 individuals of Fopius arisanus (also previouslyreleased against C. capitata). In 2009 the total parasitism rate reached 25.6%.

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