Evaluation of Dispensers Containing Trimedlure, the Attractant for the Mediterranean Fruit Fly (Diptera: Tephritidae)1

Abstract

The objective of this study was to evaluate a cotton wick dispenser in comparison with controlled-release dispensers of Trimedlure (TML) (a blend of tert -butyl esters of 4- and 5-chloro-2-methylcyclohexanecarboxylic acids), which are designed to extend the time of biological effectiveness. Measurements of residual TML contents of dispensers aged in traps for known time periods showed that cotton wicks released TML at a considerably faster rate when pure TML was used than when a mixture of TML in high-boiling extenders (called Capilure®) was applied to the wicks. The polymeric membranes of plastic laminate dispensers and Biolure cups were found to slow the release of TML. As a result of this reduced amount of volatilized TML, the controlled-release dispensers of TML attracted fewer insects than did the TML/cotton wicks for the first 1 to 2 weeks of the test. However, a laminate dispenser was found to attract for a longer period of time. The release rates were temperature dependent. Biolure cups and rubber septa were unsatisfactory as TML dispensers. Commercial TML is principally (90–97%) a mixture of the four trans- isomers which vary in volatility and biological activity. Although the evaporation rates of the four isomers are not identical, major changes in isomer composition did not occur during the evaporation of TML from the laminates. Some preferential release of the more volatile isomers was shown to occur on the cotton wicks, but only after most of TML had evaporated.