Study of chromatic attraction of the red palm weevil, Rhynchophorus ferrugineus using bucket traps

Rhynchophorus ferrugineus (Olivier) (Coleoptera Dryophthoridae) is at present considered the biggest threat to palm trees worldwide. Due to the current trend towards the use of environmentally-friendly control measures, increasing interest is being shown in trapping as a way of dealing with this pest. The present study assessed the influence of chromatic attraction on the capture of R. ferrugineus adults and identified possible reasons for the better performance of pheromone traps. Two tests were carried out using coloured bucket traps; in the first the traps were baited with male aggregation pheromone and kairomone from R. ferrugineus, while the second involved traps without olfactory attractants. The spectral reflectance of the colours tested and of leaves and external trunk fibres from the Phoenix canariensis (Hort. ex Chabaud) were measured by spectrophotometer. The internal climatic conditions of the coloured traps were also analysed. Black traps, both with and without olfactory attractants, captured significantly more R. ferrugineus adults than red and white traps. The higher efficacy of the black traps was mainly due to chromatic attraction and not only to the possibly higher emission of olfactory attractants. The olfactory attractants used to bait traps are responsible for the female-biased captures, a phenomenon found to occur with all the colours tested. This study provides useful information for improving current management strategies against R. ferrugineus.