Mixture of 2-Phenylethanol and n-Valeric Acid, a New Attractant for the Onion and Seed-Corn Flies, Hylemya antiqua and H. Platura : Diptera : Anthomyiidae

Abstract

Acidic fraction of the extract of decomposing onion pulp, which is a potent attractant for the onion and seed-corn flies, Hylemya antiqua and H. Platura, was analyzed by GC-MS and shown to contain acetic, propionic, iso-butyric, n-butyrc, iso-valeric and n-valeric acids. These organic acids, except acetic acid, showed a weak attractancy to the seed-corn fly, but little to the onion fly. Some of the acids showed synergism with 2-phenylethanol. Since n-valeric acid enhanced the attractancy of 2-phenylethanol most significantly and stably, this compound was chosen as a synergist in further studies. Optimum concentrations of 2-phenyl-ethanol and n-valeric acid as a water solution were estimated to be 0.2% and 0.05%, respectively. Comparison of attractancy between decomposing onion pulp and 2-phenylethanol+n-vakeric acid mixture showed that the latter was superior to the former by 1.8 to 5.0 times in capturing onion fly and by 3.7 to 5.7 times in the seed-corn fly. This chemical attractant may be applicable in monitoring the occurrence of Hylemya pests.