A microscopic insect, just hatched, crawls out of a bird feather and sinks its mouthparts into the base of a hemlock needle. The hemlock woolly adelgid (HWA) feeds on sap. Its life cycle mimics that of all insects: hatch, eat, reproduce, and die. What differs here is that HWA destroys eastern hemlock stands.

[Related: Hemlock Woolly Adelgid monitoring workshop.]

Why does HWA strongly impact eastern hemlock?

HWA is an Asian native. It reached the United States in the early 1950s. It thrives in this region with no natural predators, such as parasites, to keep its numbers in check. Additionally, hemlocks here have not built up natural defenses to such an attack.

HWA forms a huge invasive population that threatens to damage and forever change Vermont’s forests.

Its arrival and spread reflect human movements and behaviors in an interconnected world. Humans are still HWAs’ primary vector into new areas. While adelgids can hitch rides on bird feathers and feet, new infestations are frequently traced to firewood and nursery stock.

HWA first appeared in Vermont in 2007. HWA has been located primarily in Windham County, with small populations in Bennington and southern Windsor Counties. Given the climate and prevalence of hemlock in the Champlain Valley, this is the next place it may spread to.

A group effort:

Fortunately, many government agencies are involved in detection and monitoring efforts, eradication schemes, public education, and research on the insects’ biology and impact.

Public awareness is our most powerful tool. Armed with awareness, visitors can buy firewood locally when they travel, contact a professional if they suspect they’ve found an insect or its sign, and serve as “eyes on the ground.” Every detection nationwide has stemmed from a private citizen finding and reporting something suspicious; false alarms are preferred to undetected invasions.

What can you look for?

The hemlock woolly adelgid gets its name from the white, waxy “wool” that it coats itself with for protection. This is the giveaway for the tiny invader. Infested trees often have a “snowy” appearance from the white fluff on the adults’ bodies, which are clustered on the twig, at the base of the underside of the needle. Infested hemlocks also exhibit needle die-off during the growing season. The best time to look for HWA is from November to March.

Join us on February 29, 9 AM-12 PM, in Bristol to learn more about HWA, how to identify and monitor it, and how to slow the spread of this insect. (Find event details here.) Please pre-register by February 24, as space is limited.