Efficacy of local strains of entomopathogenic Beauveria bassiana (Bals.) Vuill. and Steinernema feltiae (Filipjev) on the pronymphs and eonymphs of Cephalcia tannourinensis (Chevin) under laboratory conditions.

The Lebanese web spinning cedar sawfly, Cephalcia tannourinensis (Chevin), is the main cedars defoliator in Lebanon. The study is to determine the effectiveness, competition and the host finding ability of two indigenous entomopathogens; a fungi Beauveria bassiana (Balsamo) and a nematode Steinernema feltiae (Filipjev) under laboratory conditions. The study included also the use of a commercial entomopathogenic nematode heterorhabditis bacteriophora (Poinar). The study targeted the two diapauses stages of the cedar sawfly, the pronymphs, and the eonymphs. One dose of the entomopathogenic nematodes and two doses of the entomopathogenic fungi were applied as well as, mixtures of the two. Local strain of B. bassiana caused mortalities of 60 and 53% on the pronymphes when applied at 50 and 500 spores/larvae, respectively. A synergistic effect was proven when the treatment consisted of two mixtures of the entomopathogens, B. bassina and S. feltiae / H. bacteriophora, and caused mortalities of 100% on the pronymphs and 86.6 to 100% on the eonymphs. The host finding ability was higher for the
entomopathogenic nematode than for the entomopathogenic fungus. The use of a combination of entomopathogens proved to be more effective when only one is used. The local strain of B. bassiana when used at the dose of 500 spores/larvae was effective.