CHEMICAL ECOLOGY OF THE PALM WEEVIL RHYNCHOPHORUS-PALMARUM (L) (COLEOPTERA, CURCULIONIDAE) - ATTRACTION TO HOST PLANTS AND TO A MALE-PRODUCED AGGREGATION PHEROMONE

Attraction to host plants by adult Rhynchophorus palmarum (L.) palm we evils was studied in the field and in the laboratory. Chemical analysi s revealed the presence of ethanol and ethyl-acetate in stems of coco palms and in pineapple fruits and of pentane, hexanal, and isopentanol in coco stems. In the olfactometer, the first two compounds and isoam yl-acetate were attractive to the insects and the last three compounds , although not attractive by themselves, increased attractiveness when mixed with the first two compounds. Mixtures of these compounds, in p roportions similar to the one occurring in attractive plant tissue, we re as attractive as natural coconut tissue. In the field, the chemical compounds, either presented alone or as a mixture, did not attract th e weevil. Males produce an aggregation pheromone when smelling ethyl-a cetate. Rhynchophorol, 2(E)-6-methyl-2-hepten-4-ol, the known active c omponent of the aggregation pheromone, attracts weevils in the olfacto meter and in the field only if plant tissue, ethyl-acetate, or the abo ve-mentioned odor mix are present. We propose that a complex mix of et hanol, ethyl-acetate, pentane, hexanal, isolamyl-acetate, and/or isope ntanol serve as a short-range orientation cue to fresh wounds on the p lant and that additional host odors, attracting weevils from a distanc e, have still to be discovered. Rhynchophorol can be considered to be a synergist, having an anemotactic action at a distance. We recommend the use of retention traps baited with rhynchophorol, ethyl-acetate, a nd sugar cane as an alternative control method for the pest.