The Influence of Repellency on the Efficacy of Blatticides. III. Field Experiments with German Cockroaches with Notes on Three Other Species1

Abstract

Boric acid powder, applied at dosages of from 0.18 to 2.27 kg per dwelling and from 1.45 to 22.7 kg per commercial building, resulted in better control of the German cockroach, Blattella germanica (L.), than such representative organic insecticides as Baygon® (O-isopropoxyphenyl methylcarbamate), diazinon and diazinon plus dichlorvos, applied as liquid sprays at the usual dosages. It was more, effective also than Drione® (1 % pyrethrins, 10% technical piperonyl butoxide, 38.12% amorphous silica aerogel, 1.88% ammonium fluosilicate, 49% petroleum base oil), or sodium fluoride applied as dusts. Its greater efficacy was believed to be principally the result of its much lower repellency to cockroaches, although its longer residual activity, when compared with the organic insecticides, was probably also important. The relative superiority of boric acid increased in complex environments such as buildings of loose construction with excessive furnishings and clutter, where much untreated harborage existed. Boric acid acted as a contact and stomach insecticide. It killed cockroaches slowly, and in heavy infestations a few insects could be seen for as long as 7-10 days following treatment, but it had less tendency than other insecticides to drive the insects to previously uninfected parts of a building. In some heavy infestations in dwellings, rapid knockdown of cockroaches was accomplished by first treating the kitchen and other heavily infested areas with pyrethrum aerosols or with base oil-pyrethrum solutions with electric fogging devices. Dusting with boric acid in commercial buildings was usually followed by mopping the floors with I cup of granular boric acid added to the usual rinse water. With the exception of trisodium phosphate, the detergents normally used did not detract from the insecticidal efficacy of the solution.