The Relative Effect of Several Pyrethrum Synergists in Fly Sprays Containing Allethrin

Abstract

Sprays containing allethrin or pyrethrins in the proportion of 10 times as much adjunct as of insecticide were tested against Musca domestica by the turntable method. Piperonyl butoxide synergized pyrethrins more effectively than it did allethrin, the mixed spray with the natural insecticide being about 13 times as toxic as pyrethrins and the mixed spray with the synthetic insecticide being but 2.5 times as toxic as allethrin. The synergistic effect of n-propylisome was about 3 times as great with pyrethrins as with allethrin. Synergist 264 was not so effective as piperonyl butoxide, increasing the effectiveness of the spray by 2/3 when included with pyrethrins and by 1/3 when included with allethrin. The greater toxicity of allethrin affects the relative effectiveness of the materials, which falls in the following ascending order: (1) Pyrethrins, (2) pyrethrins plus synergist 264, (3) allethrin, (4) allethrin plus synergist 264, (5) pyrethrins plus n-propyl isome, allethrin plus n-propyl isome, and allethrin plus piperonyl butoxide, and (6) pyrethrins plus piperonyl butoxide.