AGGREGATION PHEROMONE OF COCONUT RHINOCEROS BEETLE, ORYCTES-RHINOCEROS (L) (COLEOPTERA, SCARABAEIDAE)

Male coconut minoceros beetles, Oryctes rhinoceros (L.), produce three sex-specific compounds, ethyl 4-methyloctanoate, ethyl 4-methylheptan oate, and 4-methyloctanoic acid, the first of which is an aggregation pheromone. Synthesis of these compounds involving conjugate addition o f organocuprates to ethyl acrylate is reported. In field trapping expe riments, (4S)-ethyl-4-methyloctanoate and the racemic mixture were equ ally attractive and 10 times more effective in attracting beetles than ethyl chrysanthemumate, a previously recommended attractant. Ethyl 4- methylheptanoate was as attractive as ethyl chrysanthemumate and more attractive than 4-methyloctanoic acid, but further studies are require d before it can be classed as an aggregation pheromone. Compared to et hyl 4-methyloctanoate alone, combinations of the three male-produced c ompounds did not increase attraction, whereas addition of freshly rott ing oil palm fruit bunches to pheromone-baited traps significantly enh anced attraction. With increasing dose, captures of O. rhinoceros incr eased, but doses of 6, 9, and 18 mg/day were competitive with 30 mg/da y lures. Newly designed vane traps were more effective in capturing be etles than were barrier or pitfall traps. Results of this study indica te that there is potential for using ethyl 4-methyloctanoate in operat ional programs to control O. rhinoceros in oil palm plantations.