Current practice in dwarf mistletoe infested black spruce stands calls for eradication of all trees taller than 5 ft. In a stand harvested 36 years ago, fewer than 1 tree per acre taller than 3 ft remained. Since that time, Arceuthobium pusillum has survived and spread to new areas of the stand. From 16 infected trees per acre, the population has increased to 173 infected trees per acre in 1998. As establishment of new seedlings declines, the proportion of infected trees will increase greatly. The projected spread of dwarf mistletoe, and the resulting mortality of black spruce during the remainder of the rotation will cause unacceptable yield losses. Eradication of all black spruce after harvesting is necessary to prevent serious losses from dwarf mistletoe infestation in the new stand.