Efficacy of Entomopathogenic Nematodes and Fungi as Biological Control Agents against the Cotton Leaf Worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Pathogenicity of the two entomopathogenic nematodes, Heterorhabditis bacteriophora Poinar (HP88 strain) and Steinernema riobrave and two fungi; Metarhizium anisopliae and Beauveria bassiana as well the combined effect of both against 3rd instar larvae of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) was studied under laboratory conditions. Data revealed that the tested nematodes differed in their efficacy against 3rd instar larvae of S. littoralis. The LD50 values for S. riobrave reached 438.8 and 180.1/ IJs ml/100g diet indicated the most potent nematodes at 48 and 72 h post treatment, respectively. On the contrary, LC50 reached 584.5 and 199.2/ Hs ml/100 g diet, for H. bacteriophora, respectively. The LC50 values of fungus, B. bassiana revealed least mortality percentage (7.84 x 10(11)pores ml(-1)), while M anisopolie was the most potent (2.89x 10(8)spores ml(-1)) after 7 days of treatment. Probit regression lines for the combination of the tested concentration of fungi and nematodes (B. bassiana+HP88) and (M. ansoplae + S. riobrave) against 3rd instar of S. littoralis showed that highest larval mortality increased with increasing fungal spores and/ or nematodes juvenile's concentrations.