Department or Program


Second Department or Program

Environmental Studies


Hemlock woolly adelgid (Adelges tsugae; ‘HWA’) is an invasive insect that feeds upon the foliage of eastern hemlock (Tsuga canadensis) trees typically causing mortality in four to fifteen years. In the spring of 2015, HWA was discovered at Bates Morse Mountain Conservation Area (BMMCA) and current research aims to reveal the present extent of infestation and quantify morphological and physiological responses of hemlocks to infestation. Roughly 70% of the hemlocks within the primary grove were monitored for HWA density and extent of defoliation. Micro core samples and branch samples were collected to measure the hydraulic weighted mean diameter (HWMD) of current year growth and the average length of new growth. These findings were then analyzed for their relationship with features of hemlocks themselves and of the landscape. HWA density was highest among superstory trees and increased with proximity to the road. There was no significant difference in HWMD or new growth among infested and healthy trees, suggesting either HWA was introduced recently to the area or that the cold temperature of the northern climate hinders its survival and thus ability to impact host physiology. Results serve as a baseline for continued monitoring of HWA spread and hemlock decline, contribute to research on the negative impact of HWA on eastern hemlock trees, and help spread awareness about the presence of HWA in Maine.

Level of Access

Restricted: Campus/Bates Community Only Access

First Advisor

Holly Ewing

Date of Graduation


Degree Name

Bachelor of Arts

Number of Pages


Components of Thesis

1 pdf file


Available to Bates community via local IP address or Bates login.