Devices releasing antiaggregation pheromones, such as MCH (3-methyl-2-cyclohexen-1-one) and verbenone (4-methylene-6,6-dimethylbicyclo(3.1.1)hept-2-ene), are used experimentally to manipulate destructive populations of bark beetles. Two slow release devices, bubble caps attached to boles of trees and granular beads placed on the ground, were tested in forests of California, Oregon, and Alaska to determine their release rates. The hypothesis was that ambient air and soil temperatures were major

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... eterminants in the release rates of the releaser devices. Release rates of both bubble caps and beads differed greatly. The fastest rate was for bubble caps at a warm, California pine (Pinus spp.) site where it was 15 times faster than the rate at a cool Sitka spruce (Picea sitchensis Bong. Carr.) site in Alaska. Beads released MCH quickly and were rendered ineffective in less than 2 weeks. Little or no release occurred thereafter, regardless of the amount of pheromone remaining in the bead, or litter layer temperature. Release rates determined under field conditions are useful for the field entomologist and are vital to the development of models for semiochemical dispersion.