The oak's decline in Apulia Region (Southern Italy) affects also the Quercus trojana Webb. (=Q. macedonica A. DC.), periodically damaged by numerous species of phytophagous insects that further increase existing decay processes. Observations carried out on Quercus trojana oak-grooves in Apulia during the period 1984-1990 demonstrated that, among the Lepidoptera Tortricidae on Q. trojana, the most dangerous were Tortrix viridana L. and Aleimma loeflingiana L. while Archips crataegana (Hb.) was less dangerous. Tortrix viridiana populations were more numerous than the A. loeflingiana and A. crataegana ones. The composition and the activity of parasitic complex during the outbreak of T. viridana, A. loeflingiana and A. crataegana were studied and the following larval and pupae parasitodies complex were found. -from larvae: Apophua cicatricosa (Ratz.), Scambus annulatus (Kiss.) Scambus calobata Grav. (Hymenoptera Ichneumonidae); Apanteles sp. (laevigatus Nixon group) Apanteles spp., Macrocentrus linearis Nees, Macrocentrus thoracicus Nees, Microdus dimidiator Nees (Hymenoptera Braconidae); Goniozus sp. (Hymenoptera Bethlidae); Hexamermis albicans (Von Siebold) Pol. e Art. (Nematoda Mermithoidea); Nosema spp. (Protozoa Mirosporida); NPV (Baculovirus); Entomophthora sp. (Zygomycota Entomophthorales); - from pupae Brachimeria intermedia (Nees) (Hymenoptera Calcididae); Itoplectic maculator Fabr., Itoplectic alternans Grav., Apechthis rufatus Gmelin, Phaeogenes invisor Thumb. (Hymenoptera Ichneumonidae); NPV (Baculovirus); Beauveria bassiana (Vuill.) Balsam. (Dauteromycotina: Hyphomycetes). Macrocentrus linearis from T. virdana larvae and Microdus thoracicus from A. loefingiana larvae were found for the first time on all areas in Italy; and for the first time in Southern Italy: Apophua cicatricosa, Scambus annulatus and S. calobata from T. viridana larvae, already found in Sicily and Sardinia. In addition to these parasitoides the fungus. Beauveria bassiana was found for the first time as parasite of the pupae of T. viridana, A. loefingiana and the presence of a NPV, of the Nematode Hexamermis albicans, and of the Protozoa Nosema spp. was also confirmed in other Q. trojana oak areas. The Nematode H. albicans that has often parasitized numerous Lepidoptera larvae living on Q. trojana, demonstrated preference for T. viridana larvae and together with Nosema spp. has effectively cooperated with parasitoids in reducing Lepidoptera populations, while NPV and Entomophthora sp. and B. bassiana fungi were less effective.