Age-Specific Reduction in German Cockroach (Blattoidea: Blattellidae) Populations Exposed to Diflubenzuron2

Abstract

The chitin synthesis inhibitor, diflubenzuron, caused age-specific reductions among populations of the German cockroach, Blattella germanica (L.), in test arenas (122 by 122 by 30.5 cm). Diflubenzuron at 30, 60, and 120 mg A.I./m2 killed nymphs with the molting first instar the most susceptible stage, and male and female adults that were exposed as nymphs. At the higher application rates (60 and 120 mg/m2), selective mortality during the first ecdysis resulted in lower numbers of older nymphs as the original population of cockroaches placed in the arenas matured. The decline in the number of older nymphs caused a shift in population age structure to one consisting almost entirely of first instar nymphs and adults. After 12 wk of exposure, total cockroach numbers were reduced by 67.3%, 93.0%, and 98.2% with residues of 30, 60, and 120 mg/m2, respectively. Diflubenzuron residues did not reduce egg hatch.