Efficacies of Entomopathogenic Fungi from Metarhizium, Beauveria and Isaria on German cockroach, Blattella germanica (L.) (Blattaria: Blattellidae)

Blattella germanica is an important pest and able to transmit various pathogens and parasites of human, cause allergic reactions and food contamination. Due to risks and problems related to currently employed chemicals for their control, use of entomopathogenic fungi as alternative control approach has been under investigation. In this study, seven entomopathogenic fungi isolated from soil samples and five fungal isolates obtained from entomopathogenic fungal cultures have been tested against B. germanica. The fungi belong to the species Beauveria bassiana (3 isolates), Metarhizium anisopliae (4 isolates), Isaria tenuipes (1 isolate), I. fumosorosea (3 isolates), and I. farinosa (1 isolate). Conidial suspensions of all twelve isolates were applied at 1x107 conidia ml-1 concentration to ten insects in each replication. Tests were carried out at 26±2oC, 65±5% relative humidity in darkness with three replications. Eight isolates were found effective on B. germanica with mortalities varying between 60.0% and 96.7% in 14 days. The results indicated that Metarhizium isolates had the highest efficacies (83.3-95.8%) followed by Beauveria isolates (70.8-79.2%) and the isolates of Isaria had the lowest efficacies (50.0-70.8%). These isolates were as effective as the previously reported isolates of the same species with higher efficacy values. The most effective two isolates of M. anisopliae (S8-2 and S11-6) appear to be worth investigating further for developing a microbial control agent against cockroaches.