CHEMICAL ECOLOGY OF PALMS WEEVILS, RHYNCHOPHORUS SPP (COLEOPTERA)

The chemical ecology of palms weevils (Rhyncophorus spp.) was studied in the field and in the laboratory to identify substances attractive to adults and likely to improve trapping in plantations. We showed that R. palmarum adults are attracted by the odour that emanates from the tissue of their host plants during fermentation. The composition of odours emitted by 4 plants attractive to this species was determined. An aggregation pheromone was discovered and identified in R. palmarum. It is (E)-2-methyl-5-hept-en-4-ol, a compound named rhynchophorol I. Another two aggregation pheromones were identified in R. phoenicis and R. vulneratus species: these are 3-methyl-4-octan-ol (rhynchophorol II) and 4-methyl-5-nonan-ol (rynchophorol III) respectively. These molecules, which are emitted by males, act in strong synergism with plant odours to attract conspecific of both sexes from the same species. Synthetic rhynchophorol I and II (racemics) can be used to increase R. palmarum and R. phoenicis captures by a factor of 10 to 20 respectively, using conventional plant traps. Further studies on odourss from plants attractive to Rhynchophorus weevils should soon lead to the production of totally synthetic attractants, making for easier and more effective capture of these pests.