Changes in predation and parasitism of the citrus leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) populations in Spain following establishment of Citrostichus phyllocnistoides (Hymenoptera: Eulophidae)

The citrus leafminer, Phyllocnistis citrella, is a pest native to Southeast Asia which threatened the citrus industry in the Mediterranean region upon its introduction in 1993. Immediately afterward, a classical biological control program was implemented in Spain. The exotic parasitoid Citrostichus phyllocnistoides was the only introduced parasitoid to become established. In 2006, data on both the incidence of P. citrella and the impact of its natural enemies were collected following the same protocols used in 1997-1999 when C. phyllocnistoides was not yet present. C. phyllocnistoides constituted 99.4% of the parasitoids collected in 2006 corresponding to a decrease in the incidence of P. citrella from 3.2-5.1 to 1.8-2.4 mines per leaf in 1997-1999 and 2006, respectively. Mortality caused by natural enemies on P. citrella in 2006 was 93.3% (18.0% parasitism, 40.8% feeding punctures and 34.5% predation). C. phyllocnistoides, which preferentially parasitizes P. citrella second instar larvae, has displaced most of the indigenous parasitoids that moved onto P. citrella mainly parasitizing third instar larvae, upon its introduction. Because C. phyllocnistoides is an idiobiont parasitoid and preferentially parasitizes P. citrella second instars, this stage has become dominant in the orchards. The shift in the relative abundance of P. citrella larvae has prompted generalist predators to prey mostly on second instars and has contributed to the displacement of the native non-specific parasitoids, which principally utilize third instars, from the system. Both indigenous predators and the introduced parasitoid are key players in the natural regulation of P. citrella.