EFFICACY OF CLOSTRIDIUM-BIFERMENTANS SEROVAR MALAYSIA ON TARGET AND NONTARGET ORGANISMS

Clostridium bifermentans serovar malaysia (C.b.m.) is highly toxic to mosquito larvae. In this study, the following aquatic nontarget invert ebrates were treated with high C.b.m. concentrations (up to 1,600-fold the toxic concentration for Anopheles stephensi) to study their susce ptibility towards the bacterial toxin: Planorbis planorbis (Pulmonata) ; Asellus aquaticus (Isopoda); Daphnia pulex (Cladocera); Cloeon dipte rum (Ephemeroptera); Plea leachi (Heteroptera); and Eristalis sp., Cha oborus crystallinus, Chironomus thummi, and Psychoda alternata (Dipter a). In addition, bioassays were performed with mosquito larvae (Aedes aegypti, Anopheles stephensi, and Culex pipiens). Psychoda alternata l arvae were very susceptible, with LC50/LC90 values comparable to those of mosquito larvae (about 10(3)-10(5) spores/ml). The tests with Chao borus crystallinus larvae showed significant mortality rates at high c oncentrations, but generally not before 4 or 5 days after treatment. T he remaining nontarget organisms did not show any susceptibility. The investigation confirms the specificity of Cb.m. to nematocerous Dipter a.