Effects of successive subculturing of beauveria bassiana isolates on spodoptera littoralis

Entomopathogenic fungi has an important place in biological control programs against pest insects. They have efficiency and safety for humans and other non-target organisms. They leave less or no residue in food. They are ecologically safe, so that they are perfect candidate for using as a microbial insecticide. Soil is an important storage place for fungi and many entomopathogenic fungi are often isolated from soil. They are an important part of terrestrial ecosystems and they play an important role in the population regulation of many soil living insects. Many entomopathogenic fungi species has been commercialized as biopesticides to control insect pests. The fungi selected for microbial pesticides should have high pesticide tolerances and be able to stay alive in cropping systems. In addition to effectiveness of entomopathogenic fungi in the mass production of fungal biopesticides, it is important to maintain their virulence in vitro successive subculturing. Many entomopathogenic fungi tend to lose their virulence and spore production in vitro subculturing. In this study, the effect of 12 successive in vitro subcultures of four pathogenic strains of Beauveria bassiana (BMAUM-E2001, BMAUM-E2003, BMAUM-E6001 ve BMAUM-M6001), isolated from soil in Isparta province and districts in 2014 was studied on Spodoptera littoralis, an important pest of cotton and vegetable cultivation. In addition to that, colony development and spore germination of each subcultures was evaluated on artificial media. Subculture forms of all isolates except BMAUM-E2001 isolate were found to be highly virulent on S. littoralis larvae and caused 100% death in 5 days. The mycelial growth of 1-12th subcultures showed a linear gradient in time. Even in the last 12th subculture, the isolates did not lose their virulence and completed their development and spore production.