PS 74-182 - Interaction of visual and olfactory cues in Rhabdoscelus obscurus (Coleoptera: Curculionidae)

Thursday, August 6, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Gadi V.P. Reddy, Zerlene T. Cruz and Fritz Naz, Western Pacific Tropical Research Center, University of Guam, Mangilao, Guam

The New Guinea sugarcane weevil, Rhabdoscelus obscurus (Boisduval) (Coleoptera: Curculionidae) is a native of New Guinea and the adjoining islands It was originally described from specimens collected in New Ireland, Papua New Guinea and has since spread to many islands in the Pacific, including Australia and Indonesia. Dispersal of the weevil was almost certainly associated with inter-island trading of sugarcane in earlier years, but more recently palms introduced for the ornamental horticultural industry have become the most favored hosts for this weevil. On Guam, R. obscurus is a major pest of ornamental and other palms such as coconut palm (Cocos nucifera L.), betel nut (Areca catechu L.), champagne palm (Hyophorbe lagenicaulis, pritchardia palm (Pritchardia pacifica), pygmy date palm (Phoenix roebelenii), Alexander palm (Archontophoenix alexandrae, royal palm (Roystonea regia and date palm (Phoenix canariensis) as well as sugarcane (Saccharum officinarum). Currently this weevil poses a serious threat to ornamental palms in the nursery industry and to betel nut production in Guam. The withdrawal of the ban on entry of betel nut into the U.S. mainland from Guam by the Food and Drug Administration has encouraged commercial cultivation of betel nut on Guam. Therefore, an effective management program for this weevil is urgently required.


Among the existing control methods of the pest, chemical application is both undesirable and expensive and biological control is so far limited. In addition, the semiochemical-based trapping method does exist but typically results in low capture rates. In this study, most interesting result of work is the influence of visual and olfactory cues on the semiochemical-based trap catches of R. obscurus. In a color-choice test, the R. obscurus clearly preferred brown traps over yellow, red, gray, blue, black, white, and green, with mahogany being more attractive than other shades of brown. Color has been shown to influence the efficacy of pheromone traps, and our results for the banana weevil show that not only is brown preferred over the other colors tested but also that mahogany is preferred to other shades of brown. The R. obscurus preference for mahogany brown did not preclude the need for a chemical attractant; however, pheromone-baited traps caught significantly higher numbers of adults than unbaited ones.

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