Although the application of entomogenous fungi as a means of mosquito control is not a novel one, its great potential has renewed sufficient interest over the past several years to generate new studies. The 4 genera of fungi most frequently studied in this regard are Coelomomyces, Entomophthora, Beauveria, and Metarrhizium.
The taxonomically more primitive Coelomomyces appear quite useful in that they are largely restricted to the family Culicidae, and they maintain themselves in the mosquito environment year after year. Natural infections by Coelomomyces and Entomophthora occur in both larvae and adults and observations indicate that significant control, under proper conditions, can be achieved. However the physical, chemical, and biological factors associated with disease induction are poorly known. The major difficulties have been in devising suitable culture methods and inducing laboratory infections.
The higher Beauveria and Metarrhizium are not normally associated with mosquitoes and thus require repeated applications for use in control. Nevertheless, these fungi are easily employed in microbial control tests largely due to their ease of culturing on any general mycological medium. Metarrhizium appears to offer more promise as a means of control for reasons discussed in the text. Toxins produced by these fungi may also have some practical interest. Preliminary experiments with filtrates of B. bassiana (Bals.) Vuill. indicated several compounds are involved and yielded an LT50 of about 12 hours with mosquito larvae. Destruxins A and B of M. anisopliae (Met.) Sor. proved toxic to 4 species of mosquito larvae, although the dosages required were much higher than for commercial larvicides.
Virtually all practical aspects of field microbial control studies remain unexplored.
