Abstract: [Objective] In order to develop effective lures that can uniformly and persistently release biologically active semiochemicals in the field, it is necessary to determine the release rates of various insect pheromones and host volatiles from different types of commonly used dispensers after the active compounds are identified.[Method] In this study, the release rates of four common bark beetle aggregation pheromone components (ipsenol, ipsdienol, trans-verbenol and S-cis-verbenol), two major Dendrolimus sex pheromone components (Z5,E7-12:Ald and Z5,E7-12:OH), and two conifer host volatiles (S-(-)-α-pinene and R-(+)-α-pinene) from four different types of dispensers were investigated under laboratory conditions (temperature, 24-26℃; relative humidity, 50%-80%; wind speed, 300 mL·min^-1) using dynamic headspace volatile collection method. The entrapped components on Porapak Q were extracted from sampling tubes with hexane and quantified by Gas Chromatography.[Results] Results indicated that ipsenol had higher release rates than ipsdienol from the polyvinylchloride bubble cap dispensers over the test period, showing significant differences for both (+) and (-) enantiomers of ipsenol and ipsdienol on day 2, 22, and 29. Ipsenol and ipsdienol released quickly in the first two days and gradually declined to the lower release level on day 15, then increased sharply during days 15-36 with a peak of release rates at the day 36, but finally declined to a consistent low release level. The closed polyethylene (PE) tube dispensers (#730) did not release any Dendrolimus sex pheromone components (Z5,E7-12:Ald and Z5,E7-12:OH) while the open PE tubes released them, indicating that these two moth pheromone components can't penetrate the 1 mm thick PE wall. The release rates of these two conifer host volatiles, S-(-)-α-pinene and R-(+)-α-pinene from the PE bottles varied over the whole testing period; with ups and downs during the earlier test period, reached the peak between 2 to 4 weeks after the start, and maintained at low level after the 43^th day. The release rates between these two components on day 15 and 29 were significantly different, even though the differences in their overall average release rates were not significant. Release rates of trans-verbenol and S-cis-verbenol from PE pouch maintained a relatively low level during the first two weeks, then increased sharply to a peak on the day 36 for trans-verbenol or the day 43 for S-cis-verbenol, and then dropped to and maintained at a low level after their corresponding peaks. trans-verbenol showed significantly higher release rates than did S-cis-verbenol throughout the testing period except at the day 43.[Conclusion] Studies of these release patterns of different semiochemicals from different types of dispensers could help us understand the dynamic releasing characteristics of various volatiles in the field, and their potential effects on the semiochemical-based monitoring and control efficacies. Finally, these results would provide some critical information on the selection of optimal dispensers for different semiochemicals in the pest control program.

Key words: semiochemicals, dispensers, release rate, gas chromatography, ipsenol, verbenol