Outcome of Insecticide Control of Cockroaches (Dictyoptera: Blattellidae) in Public Housing in France

The current situation in high-rise blocks of low-income flats in the French city of Rennes concerning cockroach (Blattella germanica(L.) ) presence and insecticide control was investigated. Based on the indications of an enquiry involving 838 flats, an improved control protocol was drawn up and applied during a 2 year campaign of insecticide treatments in 232 flats. This campaign showed that the proportion of flats where cockroaches were found was in fact lower than the proportion of flats in which during the inquiry residents reported seeing cockroaches. During the campaign we found that there was a significantly higher proportion of cockroach infested flats where residents refused treatment than could be revealed by the inquiry. During our campaign, information given to residents and precise knowledge of the cockroach situation in each flat enabled us to reduce the number of flats treated unnecessarily. However, the proportion of flats treated was still important. The results of our campaign stressed two points important for the success of a cockroach control operation using insecticides: (1) Access to all of the flats is absolutely necessary, and (2) the exact evaluation of the cockroach population in each flat is difficult, particularly for small populations.