USING PHEROMONE-BAITED TRAPS TO CONTROL THE AMOUNT AND DISTRIBUTION OF TREE MORTALITY DURING OUTBREAKS OF THE DOUGLAS-FIR BEETLE

Multiple-funnel traps baited with strong aggregation pheromone lures w ere placed throughout three 259 ha plots in northeastern Oregon during an outbreak of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopk ins. Mean numbers (I SEM) of Douglas-fir beetles collected per plot fo r the entire flight periods of 1992 and 1993 were 277,921 +/- 40,447 a nd 268,834 +/- 37,088, respectively. Mean numbers (+/- SEM) of the mos t abundant predator, Thanasimus undatulus (Say), collected per plot in 1992 and 1993 were 43,527 +/- 3,553 and 35,652 +/- 3,514, respectivel y. Douglas-fir beetle-caused tree mortality was concentrated around th e trap sites in the treated plots, even though traps were located an a verage of 40 m from the nearest host tree. Managers can influence the spatial distribution of tree mortality during an outbreak by selective placement of traps across the landscape. Selective trap placement, pl us the removal of trapped beetles from the population, may reduce tree mortality within the general area.