Intra- and inter-specific attraction of cockroach faecal extracts: studies for improving bait activity

The management of cockroach infestations in urban environment has undergone some changes in recent years by moving from the predominant use of sprays to the use of baits. Cockroaches excrete an aggregation pheromone with their frass and mark their harbourages with it. The major components of the excretory material are ammonia, methylamine, dimethylamine and trimethylamine. Only few research has been carried out till now, and no practical use of aggregation pheromone is published. This research tended to improve knowledge on cockroach chemical volatiles and their role in chemokinesis on individuals of the same species and of closely related species. We investigated the behaviour of the four sinathropic italian species (Blattella germanica, Supella longipalpa, Blatta orientalis and Periplaneta americana). Faecal extracts have been obtained directly from faeces with two different solvents: water and methanol. Results of “Y” olfactometer bioassays showed that methanol faecal extracts always give a high intraspecific attractivity, while extracts in acqueous solution showed lesser attractive power. A gel was prepared having physical characteristics such as to ensure a good resistance to dehydration, and then it was added faecal extracts obtained with methanol. Bioassays that we conducted in arena showed that the new gel containing faecal extracts was always more attractive than commercial gel formulations used as comparison. In conclusion the cockroach faecal extracts obtained with methanol, can effectively increase the attractiveness of a formulated bait, especially if combined with a gel with good texture and durability.