The Woolly Adelgid: Fuzzy yet Ferocious!

By Meghan Taber and Chrissy Nagrowski

Have you ever looked at the trees in your yard and thought they were covered in tiny pieces of wool? Those are not little cotton balls that magically appeared. They are insects! Woolly Adelgids (Adelges tsugae) are insects found in the Lehigh Valley that take on this wooly appearance. These insects are native to Japan, not the Lehigh Valley. The introduction of woolly Adelgid is something that is disputed in the invasive species community. Some argue they were introduced to the West coast in the 1920s. Others dispute that they were introduced to the East coast in the 1950s. Either way, these cute, cuddly insects are a destructive invasive species to forests. (USDA 2021).

(Blue Ridge Kitten, Flickr) CC Some Rights Reserved

 The reddish-brown eggs of the Woolly Adelgid are protected by a thick layer of fluffy wool-like waxy material.  This wax is quite sticky and can sometimes get stuck on the fur of a passing animal, allowing these hitchhikers to travel large distances. After the eggs hatch (usually in early spring) they move into the next stage of life, known as crawlers. As the name suggests, crawlers are highly mobile and are often the cause of new Woolly Adelgid infestations.  They remain in this life stage for around three months and can be found for most of the year. 

Next, the insects enter their nymph stage, where they pick a feeding spot on a hemlock tree to latch onto for the rest of their lives. Once they pick a spot, these loyal insects will insert their mouthparts into the tree and suck!  During this stage, the Woolly Adelgid starts to develop the waxy covering for which they get their name.   After a summer hibernation (estivation),  Finally all grown up, the wingless adults only live for a few weeks, with their only goal to reproduce and lay eggs!  (Maine Forest Service) (UTIA)

            This fuzzy insect’s snack of choice is the Eastern Hemlock tree. These trees are considered endangered, and their population is decreasing at an alarming rate due to the Woolly Adelgid finding their needles a feast.  This family of insects has distinguished itself for being a destructive pest and possessing some serious mouthpart hardware. Their mouthparts are thread-like and are long to allow for sucking up sap from the Hemlock tree. The adelgid sucking of the tree’s nutrients is slow and steady and takes 4-10 years to suck the life out of the tree.

A group of hemlock trees CC Some Rights Reserved USDA State Forestry

Eastern Hemlock trees are essential to the ecological systems around them. Hemlock trees grow in deep river valleys and provide shade for streams. This ecosystem becomes disrupted by the Woolly Adelgid. One research study found that the loss of Hemlock trees within the Appalachian Trail showed significant changes to eight streams. Researchers found that loss of hemlock tree canopy led to an annual increase in stream temperature and pollution.

There is a silver lining to this cloud of destruction! Even though the Woolly Adelgid causes significant damage to Hemlock trees, as scientists discover ways to let both the beetles and the trees survive! One research study looked into developing tree saplings of Hemlocks resistant to the woolly adelgids deadly suck. Using root grafting, they were able to develop a healthy crop of woolly adelgid-resistant trees with plenty of extra nutrients s to combat the wooly Adelgid’s insatiable attack of the munchies.

hemlock branch complete with wooly adelgids CC Some Rights Reserved Kathie Hodge

The woolly adelgid’s legendary appetite does not only affect the Eastern Hemlock Tree. It has repercussions on the nearby bird populations. More specifically, the black‐throated green warbler, blackburnian warbler, and Acadian flycatcher are bird species that rely on the Eastern Hemlock for their homes. These populations have experienced steep declines due to wooly adelgid invasion of their homes.

            There have been attempts to try and maintain the woolly adelgid’s chaos by introducing biological controls. The process of biological control is when a non-native species of insect is introduced into the area where the target species is, and the biological control will prey upon the target species to decrease their population. Here have been two beetle species approved to be the biological control of the Woolly Adelgid. They are Laricobius nigrinus and Laricobius rubidus. After months of allowing the beetles to establish their populations, L. nigrinus was seen to have promising results in controlling the Woolly Adelgid population. The other beetle species did not show as much of a promising result. One of the beetle species was able to establish some control over the Woolly Adelgid is promising in seeing a future where the Hemlock Tree can return to her former glory.

            The woolly adelgid has a super fuzzy exterior with questionable ulterior motives. They have some serious headgear which gives them the ability to lock on, quite loyally, to the Eastern Hemlock tree. To some, this may seem romantic, but the one-sided relationship is draining, and things generally don’t end well for the tree. The damage that woolly adelgids cause to the Northeast forest ecosystems cannot be ignored.


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