Abstract
A new long-lived formulation of a chemical attractant for the onion and seed-corn flies, Hylemya antiqua and H. platura was developed. First, the release rate of 2-phenylethanol and n-valeric acid from aqueous solutin heretofore used was estimated to be 1.4-3.5 mg/hr and 0.5-1.2 mg/hr (initial rate-final rate), respectively. Second, an attractant mixture without any dilution was encapsulated in several types of tubes, a capsule, and a bulb, and changes of release rates from these dispensers were observed for 37 days. A silicon rubber bulb was found most suitable for releasing the attractants at a high rate. Although the release rate of attractants from the bulb was observed to change slowly, the formulation (containing 2 ml attractant) was estimated to keep its initial attractancy for at least 28 days. Field trapping tests showed that the attractancy of the new formulation was comparable to that of the former aqueous form, and we concluded that this formulation of attractant in the silicon rubber bulb can be practically applied in population monitoring.
