Improvement of German cockroach (Dictyoptera: Blattellidae) population control by fragmented distribution of gel baits.

The aim of this study was to test the efficiency of gels in relation to fragmentation of baits and population density against the German cockroach, Blattella germanica (L.). We hypothesized that the efficiency of cockroach control could be improved by fragmentation of gel baits, i.e., by distributing the same amount of bait in several small drops instead of one large one. Our results show that bait fragmentation increased the number of cockroaches gaining access to the gel. However, bait fragmentation increased cockroach mortality only at high population densities. Our results allow us to recommend modulation of bait application in relation to cockroach population density. At low population densities (42 individuals/m2), the recommended dose, one single 30-mg drop/m2, can be applied. At high population densities (> or = 208 individuals/m2), the same recommended dose would be more efficient if applied as several 3-mg drops.