Further Experiments With DDT in the Control of Simulium Arcticum Mall. In the North and South Saskatchewan Rivers1

Abstract

In 6 tests during the period 1949 to 1951 single 15-minute applications of 0 1 p p m of DDT practically eliminated black-fly larvae (Simulium arcticum Mall) from the Saskatchewan River for distances up to 115 miles. Best results were obtained when the water was turbid with finely divided inorganic material Fish were killed during 2 tests in 1949, apparently because the larvicide used was heavier than water and settled as globules on the river bed and was ingested In laboratory tests with a DDT solution with a specific gravity of less than 1 0, fish were not affected by immersion for 3 hours in water containing as much as 100 p p m of DDT. The larvicide affected black-fly larvae more than other aquatic insects In 2 tests black-fly larvae were eliminated without apparent effect on other aquatic organisms DDT was extracted from suspended solids from water samples collected as far as 68 miles downstream from the point of application. At this distance, 2 26 to 0 24 μg of DDT per gram of suspended solids was ex...