Role of spontaneous plants as a reservoir of alternative hosts for Semielacher petiolatus (Girault) and Citrostichus phyllocnistoides (Narayanan) (Hymenoptera, Eulophidae) in citrus groves –

The significance of spontaneous plants for the populations of two exotic parasitoids, Semielacher petiolatus (Girault) and Citrostichus phyllocnistoides (Narayanan), was investigated in five Sicilian citrus groves. Both species were obtained from two herbs typically growing beneath the citrus trees in the period of scarce availability of the target host, the citrus leafminer Phyllocnistis citrella Stainton. S. petiolatus was reared from Cosmopterix pulcherimella Chambers, a specific leafminer on Parietaria diffusa M. et K., while C. phyllocnistoides was reared from the same species and from a Liriomyza species associated to Mercurialis annua L. These last two host records are new and further broaden the known host range of these parasitoids, previously considered as specialists. Thus, natural vegetation diversity enhances the survival and maintenance of S. petiolatus and C. phyllocnistoides in citrus agroecosystems providing them with alternative hosts. Moreover, the incidence of parasitism of the two exotic parasitoids on non-target hosts was so low that a negative impact both on native leafminers and autochthonous parasitoid populations can be excluded.