An Observation on Virulence of Mosquito-killing Fungus, Pythium guiyangense after Rejuvenated through Its Host, Culex quinquefaciatus Larvae

To observe the virulence of mosquito-killing fungus, Pythium guiyangense Su (Pg) after being rejuvenated through its host, Culex quinquefaciatus larvae. Bioassay was conducted by adding Pg mycelia with its host C. quinquefaciatus larvae into disinfected plastic containers, recording numbers of dead and infected larvae, and calculating mortality rates and infection rates. Pg was re-isolated from infected larvae using KPYG2, SFE and water agar plates, and used to infect C. quinquefaciatus larvae again. The mortality rates and infection rates, specially infection rates in groups and in individual containers were calculated and compared. After several cycles of continuous rejuvenation, C. quinquefaciatus larvae infection rates by Pg increased markedly, including the highest group infection rates and the highest and lowest infection rates in individual containers, which were generally up to 40% or above, specially, infection rates of 100% were achieved in individual container. Rejuvenation through host is an effective way to increase virulence of Pg to mosquitoes.