Tests with DDT to Control Black Fly Larvae in Alaskan Streams1

Abstract

In May 1949 sprays containing 20% of DDT and other ingredients (40% of Velsicol AR-50 [chiefly mono- and dimethyl-naphthalenes] and 40% of fuel oil) were applied by airplane to the Naknek River and its tributaries near Naknek, Alaska, at a rate of 0.1 lb. of DDT/ acre. The treatments caused detachment of small larvae but had little or no effect on the large overwintering larvae. Similar treatments to the same streams in late June gave complete control of all stages of new-generation larvae. Hand applications made in the 3d week of May at 0.3, 0.5, and 2 ppm. for 15 min. caused only 22, 29, and 60% detachment of overwintering larvae in a stream, whereas at similar temps. (42[degree], 50[degree], and 62[degree] F) in July and Aug. of.previous seasons, 0.4 ppm. was completely effective against new-generation larvae.