Natural control factors are normally relied on to hold destructive insects below the level of economic damage. When insect control is attempted every effort should be made to prevent injury to beneficial parasites and predators.

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, is an important enemy of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Present control practices for the Douglas-fir beetle consist of rapid cutting, transportation, and milling of infested trees so that beetles will be destroyed in the slabs before they emerge to infest other trees. During these operations, natural control agents are often inadvertently destroyed along with the beetles. Because of this fact serious beetle infestations may be unnecessarily prolonged. Detailed knowledge of the life history of the narural control agents and of the effect of logging and milling practices on the populations of beneficial parasites and predators is needed before control practice recommendations, which may be less destructive to the beneficial insects, can be set forth.