ETHYL PROPIONATE - SYNERGISTIC KAIROMONE FOR AFRICAN PALM WEEVIL, RHYNCHOPHORUS-PHOENICIS L (COLEOPTERA, CURCULIONIDAE)

Small trunk pieces of a freshly felled 10-year-old oil palm, Elaeis qu ineensis (Jacq.), were placed in a modified Nalgene desiccator, and vo latiles captured for six days on Porapak Q. Gas chromatographic (GC) a nalysis of Porapak-Q-trapped volatiles with both flame ionization (FID ) and electroantennographic detection (EAD) using male or female R. ph oenicis antennae revealed several EAD-active compounds. They were iden tified as: ethyl acetate, ethyl propionate, isobutyl propionate, ethyl butyrate, and ethyl isobutyrate. In field experiments in the La Me Re search Station, Cote d'Ivoire, ethyl propionate (50 mg/24 hr) but not all esters combined (50 mg/24 hr each) significantly increased capture of R. phoenicis in pheromone-baited (3 mg/24 hr) traps. One kilogram of 1- to 3-day-old palm tissue was significantly more effective than e thyl propionate in enhancing pheromone attraction. Superior attraction of palm tissue may be attributed to additional as yet unknown semioch emicals. Alternatively, release rates and/or ratios of synthetic volat iles differed from those of palm tissue at peak attraction.