Summary of Hemlock Canker in Southeast Alaska

Source: Forest Health Conditions in Alaska reports (1969-2012)

  • The first reported hemlock canker outbreak occurred on Prince of Wales Island in 1973 with an estimated extent of 3000 acres. This outbreak was closely followed by severe disease near Edna Bay on Kosciusko Island in 1974 and 1975, concentrated along logging roads and in young-growth stands harvested in the 1940s. In 1977, disease occurred on Prince of Wales Island from Thorne Bay to Control Lake.
  • Another outbreak occurred on Prince of Wales and Mitkof Islands 1985-1986, mapped along more than 35 miles of roadside forest.
  • The next flare-up on Prince of Wales Island began in 1990; by 1992, this outbreak had been mapped across more than 60 miles of roadside forest, and new outbreaks were reported near Rowan Bay on Kuiu Island, Corner Bay on Chichagof Island, and Carroll Inlet on Revilla Island, finally subsiding around 1994.
  • In 1998-1999 hemlock canker was observed in several roadless areas, and was again common on the Rowan Bay road system on Kuiu Island and the western arm of Cholmondeley Sound on Prince of Wales Island. In 2001, several small hemlock canker flare-ups were noted and mapped along roadsides and shoreline areas of central Prince of Wales (Cholmondeley Sound) and Etolin Islands. This outbreak continued to build in 2002, affecting some areas far from roads, and also causing mortality of second-growth crop trees in thinned timber stands near Polk Inlet. This outbreak diminished and there was a lull in hemlock canker activity until 2012.

Content prepared by Robin Mulvey, Forest Health Protection, rlmulvey@fs.fed.us

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