Influence of Trap Type, Size, Color, and Trapping Location on Capture of Rhabdoscelus obscurus (Coleoptera: Curculionidae)

Abstract The New Guinea sugarcane weevil, Rhabdoscelus obscurus) (Boisduval) (Coleoptera: Curculionidae), is a pest of palm plantations, ornamental nurseries, and sugarcane (Saccharum L.). Field and laboratory studies have explored the effects of trap characteristics such as design, size, color, visual and olfactory cues, and location on capture of R. obscurus in date palm plantations and ornamental nurseries at five locations (Dededo, Mangilao, Malojloj, Inarajan, and Yigo) on Guam, USA. Ramp and ground traps captured similarly, and both captured significantly more adults than bucket and pitfall traps. For economy and ease of handling, the ground trap was used for all further experiments. Larger ground traps (≥40 by 25 cm) were more efficient than smaller traps (30 by 15 cm) in capturing adults in the field. Of the eight trap colors tested in the field, brown proved most effective, followed by, in order, yellow, red, gray, blue, black, white, and green; russet was more effective than other shades of brown. Mixing paint of the other colors with brown paint did not significantly improve its performance. In contrast, laboratory color-choice tests indicated R. obscurus preferred black traps over those of other colors and showed no preferences among different shades of black. Again, mixing paint of the other colors with black paint did not significantly improve their performance. Russet brown ground traps baited with pheromone lures caught significantly more adults than did identical traps without lures. Traps strapped to trees caught significantly more individuals than traps placed between trees or away from trees. Russet-brown ground traps 40 by 25 cm seemed to be the most effective at catching R. obscurus in the field, whereas otherwise identical black-colored traps were more efficient indoors.