This project was undertaken to develop a monitoring program for hemlock dwarf mistletoe (Arceuthobium tsugense, HDM) in West Coast retention-harvested forests. HDM, a common parasite of western hemlock, is an important issue affecting ecosystem management and sustainable development in retention regimes with western hemlock. Retention-harvesting practices create conditions that could exacerbate spread of HDM infestations and severity of growth impacts. Data and models are needed to predict spread and effects of the parasite in retention-harvested areas, but these are lacking or require further development. Monitoring data are needed to initialize conditions for models and to provide a basis for certification programs for sustainability. The draft monitoring procedure consists of establishing an 11.28-m radius plot around the base of a residual, HDM-infected tree and recording HDM infection of the residual and newly regenerated hemlock trees in the plot. Data on HDM infection can be compared to results of previous studies to estimate rate of spread and infection.
John A. Muir.