ABSTRACT

The ability of killing cockroaches {Blattella germanica L.) by various strains of the mushroom Beauveria bassiana was studied, including also strains obtained by passaging. The study was conducted using adult insects, of varying age and sex, derived from laboratory cultures or caught in hospital rooms. The obtained results pointed out differences in the pathogenicity of B. bassiana strains for the studied populations of insects. The per cent of mortality among the insects depended on the pathogenic properties of B. bassiana strains, the density of mushroom spores in the food and on the sex of the insects. Passaging was found to be useful in case of strains with low pathogenicity for the insects since the passaged strains were more effective in Nr 3 Beauveria bassiana do zwalczania prusakow 349 their action on the insects than before passaging. Out of the studied strains the 23th strain was most effective in reducing the number of the insects.