Primary focus trees for the mountain pine beetle in the Black Hills

Abstract

During the early part of the 1991-92 attack periods of the mountain pine beetle (MPB) Dendroctonus ponderosae ponderosa pine Pinus ponderosa stands in the Black Hills of NW USA were examined for primary focus trees - the first trees attacked by the beetles. Once found, a number of characteristics were recorded for each primary focus tree. Lightning strikes, MPB pitchouts, Armillaria infections, or physical breakage were present on 58% of the primary focus trees in 1991 and on 61% of the primary focus trees in 1992. The various predisposing factors are discussed as to their relative importance and role in host selection. -Authors