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Northern Research Station
One Gifford Pinchot Drive
Madison, WI 53726
(608) 231-9318
(608) 231-9544 TTY/TDD

Hemlock Woolly Adelgid

Risk, Detection, and Spread

[image:] 2009 distribution map of hemlock woolly adelgid

Hemlock woolly adelgid (HWA) currently infests nearly one-half of the native range of hemlock in the East.  It can be found from southeastern Maine to northeastern Georgia and as far west as eastern Tennessee. The HWA continues to spread at an average rate of 12.5 km per year.  HWA has also been found in isolated locations in Vermont, Ohio, and Michigan as the result of infested nursery stock being transported from the generally infested area.  Forestry and agriculture officials have undertaken eradication efforts, and Maine, New Hampshire, Vermont, Ohio, Wisconsin and Michigan has implemented quarantines.  Reducing the rate of artificial spread and overall impact of HWA have become the primary management goals.  To improve the management of HWA, more information on its spread and factors that influence it is needed.  We also need to know if HWA will be able to survive when it moves into parts of the hemlock range where it currently is not found.  Early detection, risk assessment, and health monitoring are key to mitigating potential impacts on the forest resource. It is difficult to know the full extent of the threat at hand, especially when affected areas are difficult or impossible to access on the ground. Recently, remote sensing technologies have greatly increased the amount and quality of information that is available for landscape-scale detection, monitoring, and ecological risk modeling. This information includes abundance maps for individual tree species, detailed forest decline assessments (including pre-visual symptoms), and foliar chemical concentrations. Such remote sensing-based products, combined in a GIS platform with traditional topographic-based data layers, have expanded the tools available for managing forests threatened by pests like HWA. They may greatly enhance our ability to create spatially continuous landscape-scale models of ecosystem function and response to disturbance.

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Last Modified: 07/09/2010