BACILLUS-SPHAERICUS MOSQUITO PATHOGENS IN THE AQUATIC ENVIRONMENT

The fate of Bacillus sphaericus spores in the aquatic environment was investigated by suspending spores in dialysis bags in fresh and seawat er. Spore viability was lost more rapidly in seawater. Neither B. spha ericus nor B. thuringiensis israelensis (B.t.i.) spores mixed with pon d sediment appeared to attach to the sediment. However, rapid decrease in B.t.i. toxicity suggested attachment of parasporal bodies to sedim ent. B. sphaericus toxin settled more slowly and less completely. B. s phaericus spores fed to larvae of four aquatic invertebrates were most ly eliminated from the animal gut in less than one week. An exception was the cranefly (Tipula abdominalis) where spores persisted in the po sterior gut for up to five weeks.