Repellence of δ-nonalactone in German cockroaches of different stages, sexes, and ages

δ-Nonalactone is a cyclic hydroxycarboxylic acid ester with a six-membered ring found in several fruits and animal products for human consumption. It has shown repellent activity in tsetse flies Glossina pallidipes Wiedemann (Diptera: Glossinidae) and Glossina morsitans morsitans Westwood (Diptera: Glossinidae), as well as in first instar nymphs of the German cockroach, Blattella germanica Linnaeus (Hemiptera: Ecotibiidae). The aim of this study was to investigate the behavioral response of the German cockroach to the repellence produced by δ-nonalactone and how this behavior changes according to nymph stage, age, sex, and presence or absence of antennae. Small, medium, and large nymphs, as well as adult males and females, were exposed to δ-nonalactone-treated filter paper. Small nymphs were the most affected by the repellent effect of δ-nonalactone. No differences were observed in the response between males and females, nor in adult males aged ranging between less than 6 h to 90 days old. Likewise, no repellent effects were observed in antennectomized cockroaches. These results suggest that small nymphs of B. germanica are more sensitive to the repellent effect of δ-nonalactone than other stages. Furthermore, the response to this repellent is independent of sex and age, and its receptors appear to be located exclusively on the antennae. The present study encourages us to further our investigations on the use of δ-nonalactone in the integrated pest management of German cockroaches.