New Insights in Biocontrol Strategy against Cephalcia tannourinensis, the Principal Insect Defoliator of Lebanese Cedars

International audience; Tannourine cedars forest, dominated by cedars (Cedrus libani, Richard), suffers from native sawfly attacks, Cephalcia tannourinensis (Chevin). The current study assesses the presence of entomopathogenic nematodes (EPNs) endemic to the forest for their potential use as biocontrol agents in an integrated pest management to control C. tannourinensis. A survey was conducted using Galleria mellonella baits in fifteen selected sites taking into consideration the cedars' different habitats. One EPN species, Steinernema feltiae, as determined by morphometric and molecular analyses, was found in one site in the forest and was tested under laboratory conditions against C. tannourinensis prepupae, causing a mortality of 64% at 250 Infective Juveniles (IJs)/prepupa. In light of previous studies, Heterorhabditis bacteriophora (commercial strain) was accordingly considered for the controlled in situ experiments where the pathogenicity of this EPN was evaluated on C. tannourinensis. A concentration of 625,000 IJs/m(2) of H. bacteriophora caused a mortality rate of 85% on C. tannourinensis following inundative treatments conducted in jars buried in the forest's soil. While EPN succeeded to emerge from G. mellonella cadavers under the same conditions, no EPN emerged out of C. tannourinensis despite the high mortality percentage; also, opportunistic nematodes emerged unexpectedly out of C. tannourinensis cadavers.