Multi-century regional western spruce budworm outbreak patterns.

D endrochronology's rich tradition has foundations rooted in the works of da Vinci and MalpighF. Although the main stem of principles was developed by A.E. Douglass (see Ref. 1), one branch of dendrochronology actually pre-dates his work. The association between narrow tree rings and damage by insects, hail and frost was recognized by Hartig in Europe at the end of the last century!. The impact of spruce budworm (Chorist­ oneura fumiferana) feeding on the anat­ omy of tree rings was first described by Bailey2 in 1924. But it was not until the middle of this century that this branch of dendrochronology flowered and bore fruit for population dynamicists. Blais3 exploited these techniques in develop­ ing and extending a description of the long-term regional population dynamics of the spruce budworm in eastern North America back to the 17th century. More recently, Alfaro et al.4 correlated ob­ servational records of western spruce budworm (C occidentalis) outbreaks with reduced tree growth in British Columbia. The most recent flowering of this branch of dendrochronology is described in a paper by Swetnam and Lynchs.