Evaluation of the effect of the fungus Metarhizium anisopliae, as a biological control agent, on german cockroaches Blattella germanica

This investigation was undertaken to evaluate the potency of Metarhizium anisoplea as a biological alternative to the biological control of German cockroaches. The fungal spores were applied against the male and female German cockroach, using two bioassay methods, viz the submerge application and the injection. The data was analysed and the mean mortality was calculated in both of the treatment and control groups. The values of LC50 for the submerge application and LD50 for the injection bioassays were calculated using the probit analysis. The regression lines of mortality resposes were also compared using the R square tests. In the submerge bioassay, the data showed that M.anisopliae withLC50=5/65×106 spore/ml for the male and LC50=7/65×106 spore/ml for the female cockroaches was the effective pathogen. In the injection bioassay the fungus M.anisopliae with LD50=2/5×106 spore/insect for the male and LD50=7/65×106 spore/insect for the female cockroaches was the most effective mycopathogen. However, the comparison of pathogenic perfomence of the fungus using LC50 and LD50 values from both of the submerge and injection bioassays showed that the fungus excerts different pathogenic activity before and after breaching the cuticular barrier. It seems, that the use of the fungus in cockroach habitats can contribute to the reduction of ecological competency of the German cockroaches in their regions.