Résumé
Cephalcia tannourinensis (Chevin) is a hymenopteran sawfly attacking the Cedars of Lebanon, Cedrus libani, putting in danger the national emblem of the country since 1990s. A biological control program using a commercial strain of Heterorhabditis bacteriophora, one of the commonly used entomopathogenic nematodes (EPNs) was considered due to its high efficacy in previous in vitro experiments on C. tannourinensis (Noujeim et al., 2014). This program seeks to maintain this pest under its threshold level without affecting the ecosystem of these protected areas. In vivo experiments were conducted on C. tannourinensis larvae and the greater wax moth Galleria mellonella in jars introduced in the soil of the forest under natural conditions. Insects’ mortality is assessed in order to determine the efficacy of the in vivo experiments while the emergence rate of the EPNs shows their establishment by reproducing and finishing their cycle in the insect. EPNs’ persistence in the forest was determined 14 days after the application through the use of G. mellonella baiting technique to compare the efficacy and establishment of the EPNs in vivo to the in vitro experiments showing if the EPNs are capable of infesting, reproducing and emerging from C. tannourinensis larvae under natural conditions. The non persistence of the EPNs will explain the results of a previous prospection in this ecosystem where the non-detection of this parasite proves that it is not indigenous to the area of study (Noujeim et al., 2011).