Radial growth in grand fir and Douglas-fir related to defoliation by the Douglas-fir tussock moth in the Blue Mountains outbreak.

Radial growth reduction related to amount of tree defoliation was studied following a severe tussock moth outbreak. Growth sharply declined the year after defoliation began, and amount of decline was proportional to percent defoliation. Growth recovery began the year after defoliation ceased and radial increment had returned to pre-outbreak levels 5 years after defoliation.