FIELD AND LABORATORY STUDIES ON PATHOGENICITY OF FUNGUS BEAUVERIA BASSIANA TO 3 GENERA OF MOSQUITOES

The ability of the fungus Beauveria bassiana to kill mosquito larvae, adults, and eggs was challenged with Culex tarsalis, Culex pipiens, Anopheles albimanus, Aedes aegypti, Aedes sierrensis, and Aedes nigromaculis. B. bassiana was found most effective in killing larvae when applied as a conidial dust to the surface of the water. This was attributed to the primary sites of invasion being the perispiracular lobes of the larval siphon. During May and June of 1966, the mortality of C. pipiens larvae in outdoor test ponds ranged from 70% to 95% following an application of 3 lb. of viable conidia per acre. The Anopheles and Culex larvae tested all proved to be susceptible to the fungus while the Aedes larvae were not. In laboratory tests against the adults of C. tarsalis, C. pipiens, A. aegypti, A. sierrensis, A. nigromaculis, and A. albimanus, conidia of B. bassiana produced 100% mortality within 5 days after exposure, while less than 50% occurred in corresponding controls. Outdoor tests against the adults of A. nigromaculis in screen cages were less successful, yielding only 58% mortality. In this case, the fact that adults rested on the screen walls of their test cages, rather than in the dusted grass that had been provided, may explain the low mortality. Eggs of Culex and Aedes exposed to the conidia of B. bassiana hatched normally. © 1968.