Salts and the infectivity of Romanomermis culicivorax

The effects of common inorganic ions found in freshwater on the infectivity of Romanomermis culicivorax and the survival of its host, Culex pipiens, were tested. In general, the median lethal concentrations found for R. culicivorax were greater than the reported median concentrations of these ions in freshwater but less than the reported maximum natural concentrations. The ion toxicity for R. culicivorax (on a molar basis) increased in the following order: sodium < potassium < calcium; aml chloride < carbonate = sulfate < nitrate < nitrite < phosphate. The larvae of C. pipiens were generally 20 to 75 times as tolerant of higher ion concentrations as were the preparasitic stages of R. culicivorax.