Effect of Additives on the Evaporation of the Most Active Isomer of Trimedlure, the Attractant for Ceratitis capitata (Diptera: Tephritidae)1

Abstract

Trimedlure (TML) is a synthetic attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This work describes the biological activity of and the evaporation of TML from cotton wick dispensers treated with the most active of the eight isomers, TML-C, both alone and mixed with additives to facilitate delivery of this solid isomer. Field bioas say and chemical analyses were used to measure effectiveness of dispensers that had been aged as long as 10 weeks. Pure TML-C deposited as tiny crystals from an acetone solution was a highly effective and long-lasting attractant. All five additives evaluated caused an increase in the evaporation rate of TML-C but, in general, did not significantly enhance the number of flies trapped. Tetra ethylene glycol dim ethyl ether (Tet EG-DM), the least volatile of additives, yielded the smallest increase in evaporation rate of TML-G Insect catches were not significantly different in relation to TML-C evaporation rates, varying from 6 to 20 mg per day (warm weather field test) or from 3 to 10 mg per day (cool weather field test). In a laboratory test using TML enhanced in isomer C (TML- 61% C), a 5°C increase in temperature (43 versus 48°C) raised evaporation rates 1.3- to 1.7- fold. The standard TML bait currently used for C. capitata detection was significantly less effective as an attractant after 2–4 weeks of aging than was TML-C alone or with additives.