Behavioural and electrophysiological responses of the coconut pest, Rhynchophorus ferrugineus (Coleoptera: Curculionidae) to host, nonhost and alternate host plant volatiles

Abstract

Steam bark distillates of the typica and aurancica varieties of coconut (Cocos nucifera) (host plant), and of Terminalia catappa and Albizia amara (non host plants), and Areca catechu and A. concinna (alternate hosts) were subjected to electrophysiological and behavioural assays to compare attractiveness to the coconut pest, Rhynchophorus ferrugineus. In the electroantennogram (EAG) assay, the steam distillates of C. nucifera form aurancica elicited the highest response of 79.1% (relative to standard) and the form typica (young bark) 55.6%, both values being significantly different from those of T. catappa and Albizia amara (10.9 and 5.9%, resp.). EAGs of old bark (51.4%) steam distillate of C. nucifera form typica did not differ significantly from that of the young bark distillates (55.6%). The two alternate hosts, Areca catechu and A. concinna showed moderate EAG activities (29.4 and 25.9%, resp.). In a behavioural assay using an olfactometer, the steam distillates of host palms were more attractive than those of the non hosts, C. nucifera form aurancica was more attractive (79.9% attraction to the baited arm) than typica. Between young and old palms of C. nucifera form typica, no significant difference in the behavioural activity was observed. The alternate hosts showed moderate activity.