Insect infestation is a significant disturbance in the eastern and central regions of Canada where outbreaks of spruce budworm cause extensive damage to commercially valuable stands of fir and spruce. Between 1980 and 1993 over 6.6 million hectares of forest land in the eastern boreal forest was affected by the spruce budworm. Had it not been for extensive aerial spraying the affected area would have been much more extensive.