Colleen Teerling, an Entomologist with Maine Forest Service, spoke to us on February 3, 2020 about the invasive pest Hemlock Woolly Adelgid.  This pest can be found all along the Atlantic seaboard from Georgia to Maine. Colder climates, like that in Maine, causes heavy mortality of the adelgid which slows down the damage.  However, this pest continues to spread in southern and coastal Maine.
The adelgid in Maine is largely found along the coast and down peninsulas.  It does not fly, relying on birds and mammals to spread. All adelgid are female, so they do not need to mate to reproduce. The population can grow pretty quickly with 2 generations being produced each year during the warmer months.
March to July is the period of fastest spread because the “crawlers” stage of their life cycle falls in that period. These are tiny specs that can cling to hair and clothes, and can be carried on vehicles.  It is best to work on hemlock only in the fall and winter seasons to avoid spread. At a more mature stage, white patches can be found on the underside of branches both at ground level and high up in trees.
There are chemical options, but these are reserved for areas at high risk for transfer. An example is the Kittery rest area off the turnpike. Pruning can be effective, especially along driveways and walking paths to help avoid transfer. Colleen suggested trimming overhanging branches and keeping bird feeders away from hemlock trees since birds are a major source of transfer. There is also a bio-control option with the Japan Beetle, but it is quite expensive so they are put out only in small numbers. It is not a practical solution for heavily populated areas.
Colleen also shared current and proposed quarantine areas. No living trees or trimmings can be moved out of these areas. Due to the continuing spread of the adelgid, the quarantine area will be extended into Knox, Waldo and Hancock counties along the coast. These are added to the current area that extends down the coast and includes all of York, Sagadahoc and Lincoln counties, and much of Cumberland and Androscoggin counties.
Westbrook-Gorham Rotary Club will be donating the picture book At One In a place called Maine by Lynn Plourde to the Walker Memorial Library in honor of Colleen.
For more information about the Hemlock Wolly Adelgid and other insects and diseases visit the Maine Forest Service website: