The use of trap trees has become a standard practice that can be used whenever beetle populations are present or suspected. Because Douglas-fir beetles prefer freshly-downed trees to standing ones, a trap-tree program can be useful in suppressing beetle populations.

     Trap trees can be ones either cut prior to beetle flight, or standing, green trees to which pheromone tree baits have been attached. The latter have the advantage of not having to be cut before beetle flight. Either technique will contain beetles in the treated area. Trap trees can be dropped in late fall, if done sufficiently late they don't dry significantly before spring. Tree baits are best applied in the spring, prior to adult emergence. Attacking beetles are so effectively attracted to baited or felled trees, that standing green trees in the area, except for a few immediately adjacent to down or baited trees are rarely attacked. Trap trees must be removed as soon as practicable following beetle flight to be effective. Should either technique be used, and infested trees not subsequently removed, the beetle

outbreak likely would be exacerbated.
     If felled trees are used, they should be cut in groups of 3 to 5 trees. Diameters should be 15 inches or larger. Ideally, the largest, green trees in the stand should be chosen. Trees should be dropped in the shade, and left unlimbed and unbucked. Trees left in the sun, or where a major portion of the bole receives direct sunlight, do not attract beetles nearly as well as those in a shaded environment. Trees could be cut in late fall; but preferably ear1y spring, before April 1. They should be left until about mid-July, if possible. The sooner trees are removed, after beetle flight, the better. Certainly they need to be removed before the following April 1.

     Trees selected for baiting should also be among the largest, preferably in dense, shaded parts of the stand. They too, should be baited prior to April 1, left in place until after beetle flight, then removed as soon as possible.

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Forest Insect and Disease Identification and Management of Northern & Central Rocky Mountain Conifers and hardwoods