EFFECTIVENESS OF CONTROLLED-RELEASE FORMULATIONS OF MCH FOR PREVENTING DOUGLAS-FIR BEETLE (COLEOPTERA: SCOLYTIDAE) INFESTATION IN FELLED TREES

Five controlled-release granular formulations were developed that eluted 3-methyl-2-cyclohexen-1-one (MCH) in the laboratory at a rate ≥ 0.5µg/h for 60 days. Elution rate was determined by trapping gaseous radioactive MCH followed by scintillation counting. 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 just prior to Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) flight to plots containing single, freshly felled Douglas-fir ( Pseudotsuga menziesii var. glauca ) trees. Three months later, infestation by Douglas-fir beetle and other insects was evaluated. All treatments except coated corncobs and certain applications of the molecular sieve significantly reduced Douglas-fir beetle attacks. Douglas-fir beetle brood in three treatments was significantly less than in controls. Abundance of entomophagous insects was proportional to density of host beetle attacks. Douglas-fir beetle attack density was negatively correlated with degree of infestation by the scolytid Pseudohylesinus nebulosus (Lee).