• Basham, J.T.
  Great Lakes Forest Research Centre
  

Balsam fir (Abies balsamea [L.] Mill.) in three widely separated areas where trees had been dead for O to 1 and for 1 to 2 years following spruce budworm defoliation were dissected, and the extent to which stems had been attacked by secondary insects and microorganisms was studied. All trees examined 1 to 2 years after death in a stand heavily attacked by bark beetles had advanced sap rot, while trees in a stand with very little bark beetle activity had no advanced sap rot. These results agree with those of earlier studies in which a close relationship was shown between the incidence of bark beetle attack and sap rot, and in which budworm-killed trees in Ontario were consistently heavily attacked by bark beetles and were found to contain extensive sap rot when dead for longer than 1 year, whereas in Newfoundland, New Brunswick and Quebec bark beetle activity was relatively light and generally 3 to 4 years elapsed after death before appreciable sap rot developed. Current recommendations concerning safe periods in which killed balsam fir remains economically salvageable, 1 year in Ontario and 3 to 4 years in the eastern provinces, should be modified in view of these results.Bark beetle activity and sap rot development were not always related in individual trees; apparently the stand conditions that result in high bark beetle populations are also conducive to a relatively rapid rate of development of sap rot in killed trees.