Using An Algaecide To Manage Wasps Around Swimming Pools, 1979

Field tests were performed at swimming pools where Polistes wasps imbibing water were causing a sting hazard. All pools were located in San Bernardino and Riverside Counties and were treated during early September when daily high temperatures exceeded ca. 35 C. Number of wasp visits/hr and number of drowned wasps/day were recorded for 3 days before and for 3 days after additional of n-alkyl dimethyl benzyl ammonium chloride. This algaecide was applied at ca. 5 ppm, the registered dosage for control of black algae. The algaecide tested is very safe and no waiting period is required for swimmers after the algaecide is applied. Wasps alighting on untreated pool water would drink for up to 30 seconds before flying away directly toward their nests. Less than 0.1% of the wasp visits to untreated pools resulted in the wasp drowning.