The mosquitocidal activity of conidia of Tolypocladium tundrense and Tolypocladium terricola.

Tolypocladium tundrense and T. terricola UV-irradiated conidia exhibited acute toxicity to Aedes aegypti larvae in concentrations of 5 x 10(5) and 5 x 10(6) ml-1, respectively. Substances deposited on the surface of conidia following sporulation appear to be responsible for rapid intoxication and killing of mosquito larvae. Treatment of larvae with dried methanolic extract of the spores also induced a high level of mortality accompanied by the same histological changes, including vacuolization and subsequent destruction of mitochondria of the midgut cells. Cyclosporin A was identified as a predominant metabolite forming the spore surface layer.