Dataset Overview

The hemlock woolly adelgid (Adelges tsuga Annand; HWA), a small, aphid-like insect native to Japan, is currently migrating Northward through eastern North America and threatens to eliminate eastern hemlock (Tsuga canadensis (L.) Carriere), one of the most abundant, long-lived shade tolerant species, across its range. In addition, a second invasive pest, the elongate hemlock scale (Fiorinia externa; EHS), often co-occurs with HWA on hemlock with unknown long-term consequences. This study was started to analyze Hemlock tree stands, the damage created by HWA and the long term consequences of EHS.

See Full Dataset Documentation


The major objectives of this study were: (1) To characterize the pre-HWA distribution, composition, and structure of hemlock stands; (2) to characterize the spatial patterns of damage generated by HWA across southern New England since the time of its arrival in 1985; (3) to examine environmental and stand factors that are associated with declines in crown vigor and mortality of hemlock; (4) examine the dynamics of HWA and EHS in hemlock stands over time; and (5) assess whether there is a difference in the response of these insects to abiotic conditions (winter temperature, summer temperature, summer precipitation), and whether the distribution and abundance of each insect species is dependent on biotic interactions with the co-occurring insect species.

Data Collection Status

Data collection for this dataset has been completed

Start date


End date


Data Availability

This dataset is available to download from another website

Data License

Linked - Third party determines data license

Preferred Citation

Orwig D, Foster D. 2017. Landscape Response to Hemlock Woolly Adelgid in Southern New England 1997-2011. Harvard Forest Data Archive: HF081. Available at:

Update Frequency


Maintenance Plan

Not provided


  • Landscape Response to Hemlock Wooly Adelgid in Southern New England 1997-2011
  • Harvard Forest
  • Related Datasets

    Determining Dataset Similarity