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

Summary

The role spontaneous plants could eventually play towards 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 living beneath the citrus trees in the period of scarce availability of P. citrella larvae on citrus plants, and precisely: S. petiolatus was reared from Cosmopterix pulcherimella Chambers, leafminer on Parietaria diffusa M. et K., while C. phyllocnistoides on the same species and on a Liriomyza species associated to Mercurialis annua L., these last two host records being new for the parasitoid. Vegetational diversity can then enhance survival and maintenance of populations of exotic parasitoids in citrus agroecosystem, providing them with alternative hosts. The incidence of parasitism of S. petiolatus and C. phyllocnistoides on non-target hosts was, however, so low (2.8% for S. petiolatus on C. pulcherimella, and 8.3% and 3.3% for C. phyllocnistoides on C. pulcherimella and Liriomyza sp. respectively) that a negative impact on both native leafminer and autochthonous parasitoid populations can be excluded.