Susceptibility of different life stages of <i>Blattella germanica</i> (Blattodea: Blattellidae) and <i>Periplaneta fuliginosa</i> (Blattodea: Blattidae) to entomopathogenic fungi

Abstract

The susceptibility of nymphs and adults of the German cockroach, Blattella germanica Linnaeus (Blattodea: Blattellidae) and the smokybrown cockroach, Periplaneta fuliginosa Serville (Blattodea: Blattidae) to Argentinian isolates of the entomopathogenic fungi Metarhizium anisopliae (Metschn.) Sorokin (CEP 085) and Beauveria bassiana (Bals.-Criv.) Vuill. (CEP 077) was evaluated. Fungi were tested by using two different methods: bait and direct contact. Mortality was monitored daily for twenty days to obtain LT50. M. anisopliae produced 60 and 93% mortality in nymphs and adults of B. germanica, respectively, when conidia were applied by direct contact. The LT50 for adults was 3.8 days, and 8.6 days for nymphs. Direct contact of B. bassiana produced 80% mortality on adults of B. germanica with a LT50 of 4.9 days, and for nymphs 40 % mortality in 10 days. When B. germanica was exposed to bait, the level of mortality was significant in adults. Nymphs of P. fuliginosa were treated with bait with M. anisopliae and B. bassiana and they caused 50% mortality with a LT50 of 22 days, and LT50 of 27 days respectively. Nymphs and adults of P. fuliginosa treated by direct contact and adults treated with bait showed that mortality level was not significantly different as compared to the control. Results showed differences in susceptibility between the two species of cockroaches and between nymphs and adults of the same species. In addition, different responses to the fungal species with the two methods that were used in the bioassays have been demonstrated. This is the first report of susceptibility of P. fuliginosa to entomopathogenic fungi. This study demonstrates the potential of fungi as biocontrol agents against this pest.