Pyrethroid Contact Sprays Against the House Fly (Musca Domestica L.)1

Pyrethrins and 8 related compounds were tested alone and in combination, at different ratios, with a synergist, piperonyl butoxide, to determine effectiveness as contact sprays against adult house flies, Musca domestica L. The most effective pyrethroid, Roussel-Uclaf RU-11679 ( (5-benzyl-3-furyl)methyl trans-(+)-3-(cyclopentylidenemethyl)-2,2-dimethylcyclopropanecarboxylate), was 51 times more toxic than the ronnel standard; however, its effectiveness was not further potentiated by piperonyl butoxide. Four other pyrethroids were 6–10 times more effective than ronnel and were increased in effectiveness 1.3- to 6.3-fold by adding the synergist. The remaining compounds required the synergist to reach maximum effectiveness: