Abstract: A method is described for significantly reducing Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) attacks on felled trees, through the use of the Douglas-fir beetle anti-aggregative pheromone, 3-methyl-2-cyclohexen-1-one (MCH), a highly volatile and water soluble material. Controlled release formulations of MCH can prevent the buildup of outbreak population of beetles in susceptible trees. Five controlled-release granular formulations were developed that eluted 3-methyl-2-cyclohexen-1-one (MCH) in the laboratory at a rate .gtoreq.0.5 .mu.g/hour for 60 days. The inert components of these formulations consisted either of a wax-coated molecular sieve, polyethylene emulsion-coated ground corncob or dimer acid polyamide beads. These formulations and a liquid standard were applied 9 May (1975) just prior to Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) flight to plots containing single, freshly felled Douglas-fir (Pseudotsuga menziesii var. glauca) trees.