Impact of Armillaria root disease on succession in red pine plantations insouthern Ontario

Armillaria root disease created openings in southern Ontario red pine plant ations that are gradually succeeding to hardwood-dominated mixedwoods throu gh natural regeneration. A study of 13 root disease centres found several t ree and shrub species colonizing the openings. Black cherry was the most im portant hardwood and white pine the most important conifer colonizer. Morta lity of black cherry and white pine regeneration was greater than for other species. Long-term survival of conifers in the centres is doubtful, and hi gh mortality of black cherry is expected. Other hardwood species may fare b etter but with growth and yield losses due to Armillaria infection.