Bio-insecticidal Efficacy of Beauveria bassiana Vuill. Strains against Tettigonia viridissima L. in Tobacco

The green grasshopper (Tettigonia viridissima L.) is a species which attacks tobacco plants. The purpose of the present study was to establish the bio-insecticidal efficacy of entomopathogenic fungi Beauveria bassiana Vuill. strains 214, 644, and 733 on the growth and development of T. viridissima in tobacco. The research was conducted under laboratory conditions. The study found insecticidal effects of the B. bassiana strains 214, 644, and 733 against T. viridissima. Surviving of larvae was monitored at 5-day intervals until the 15th day after treatment with a spore suspension of the tested Beauveria strains. The highest virulence of the tested fungi was shown by strain 644, followed by strains 214 and 733. On the 5th day after treatment, no efficacy against T. viridissima larvae was detected. On the 10th day post-treatment strain 644 showed 66.7% efficacy, while efficacy against larvae of grasshoppers for the other two strains 214 and 733 was significantly lower: 33.3%. Efficacy gradually increased and on the 15th day post-treatment 100% mortality of T. viridissima was observed for all isolates. The results obtained from the virulence test of B. bassiana 214, 644, and 733 ascertain their application as biocontrol agents in tobacco production under field conditions.