Behavioural and electrophysiological response of sorghum chafer Pachnoda interrupta (Coleoptera: Scarabaeidae) to plant compounds

Abstract

Behavioural and antennal responses of the sorghum chafer Pachnoda interrupta (Olivier) were tested to the synthetic compounds, such as eugenol, methyl salicylate, methyl anthranilate, isoamyl acetate and butyl butyrate. In the field, all odour-baited traps, except isoamyl acetate applied on cotton dispensers, were significantly more attractive than blank (unbaited) traps and all compounds, except isoamyl acetate, elicited dose-dependent responses in both male and female antennae. Dispenser type (cotton wick or rubber septum), trap location (inside or outside sorghum fields) and season (mating/July or feeding/September) affected the performance of the different compounds as lures. In July, methyl salicylate applied on cotton was the most attractive lure, whereas the most attractive treatments in September were eugenol and isoamyl acetate on rubber septa. Possibly due to odour and visual competition from the sorghum plants, traps placed outside the sorghum fields caught significantly more beetles than traps placed inside the fields. The trapping efficiency of a locally produced trap was found not to be competitive with that of the commercially available Japanese beetle trap. Overall, the results suggest that trapping with semiochemicals has a potential in sorghum chafer management, either for mass trapping and/or as part of an integrated pest management programme.