Comparison of the Laboratory and Field Efficacy of Insecticides Used for German Cockroach Control1

Abstract

The activity of several experimental insecticides against Blattella germanica (L.) was compared with standard materials in exposure and choice tests. A formula, Potential for Effectiveness (PE), was devised to account for repellency and mortality produced by toxicants in choice tests and to rate the toxicant’s effectiveness on a scale of −100 to 100. Diazinon and chlorpyrifos provided a PE of 100. The PE of the carbamates tested ranged from 56–97. Deposits of pyrethrum and SD-43775 were toxic but repellent and the PE was −20 to 14. In field tests, 0.5% chlorpyrifos spray produced 96.7% reductions at 4 wk. Treatments with 1.1% propoxur produced 88.0% reductions, but field populations were increasing at 6 wk. Diazinon and bendiocarb spray failed to produce significant control. Cockroaches from apartments where treatments of diazinon or bendiocarb produced unsatisfactory control were 14X resistant to diazinon and 3.4X resistant to bendiocarb (μg/male). Compared to nonresistant laboratory strains, these materials were less effective against the field-collected cockroaches in choice tests. Behavioral avoidance to diazinon or bendiocarb was similar in both strains, but resistance apparently contributed to the reduced efficacy of each material.