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.

Can a Semiochemical-Based Trapping Method Diminish Damage Levels Caused by Rhabdoscelus obscurus (Coleoptera: Curculionidae)?

“…Here we provide evidence on whether semiochemical-based lures, developed recently by Reddy et al (2011), can reduce the damage caused by R. obscurus.…”

“…The addition of ethyl acetate to the pheromone lures as a synergist signiÞcantly increased trap catches of R. obscurus, but did not help in controlling R. obscurus (Reddy et al 2005). Additional studies conducted by Reddy et al (2011) to improve the capture efÞciency showed that 40 by 25-cm russet brown ground traps baited with pheromone lures and strapped to the trees are an efÞcient tool for catching R. obscurus in the Þeld. Contrariwise, the authors further reported that indoors, black, but otherwise identical, traps were the most effective.…”

“…In coconuts they bore into the base of the trunk and can weaken the tree resulting in it being blown down in high winds. In betel nut they often bore near the growing tip of the tree that can kill the tree (Reddy et al 2011). …”

“…Trapping studies conducted over several years indicate that populations are high throughout Guam (Muniappan et al 2004;Reddy et al 2005Reddy et al , 2011. As a result, Guam and other Micronesian Islands are in the midst of a decline of palms as this weevil becomes a more serious pest.…”

“…Without appropriate effective control, weevil populations are likely to cause major or complete loss of palm production in Guam and other Micronesian Islands. Moreover, R. obscurus has inßicted severe attacks on coconut trees on Guam (Reddy et al 2011). The role of monitoring is important in judging the dynamics of R. obscurus and recording area-wide population trends (Sallam et al 2004).…”