Patogenicity of Metarhizium Anisopliae and Beauveria Bassiana To the American Cockroach (Dictyoptera: Blattidae)

Abstract:
The entomopathogenic fungus Beauveria bassiana Vuillemin 1912 and Metarhizium anisopliae (Metschnikoff) Sorokin 1976 were tested against Periplaneta americana cockroach under laboratory conditions (1.1 x 106 conidia/cockroach, 24 ± 2°C and 50 ± 10% RH). The isolates tested against nymphs and adults of P. americana showed low pathogenic potential and significant mortality differences. Adults exhibited less mortality than nymphs, which showed behavioral changes once they received a conidial suspension. The two most virulent isolates were selected and tested on three representative age groups of P. americana. A second experiment evaluated if different mortality could exist in adult cockroach under controlled conditions (85 ± 10 % RH, 27°C). Cockroach adults were susceptible to infection by M. anisopliae and B. bassiana; under high relative humidity conditions these fungi caused more mortality (47%), compared with laboratory conditions (3%). Implications on the addition of these isolates to sublethal doses of boric acid are discussed.