Hemlocks are majestic. Towering, evergreen, and capable of living up to 800 years, they’ve stood like green sentinels through centuries of history. Some of the ones in Pennsylvania were probably around when Genghis Khan was still conquering stuff. They’re beautiful, shade-giving giants—and yes, the Eastern Hemlock is the Pennsylvania state tree. So naturally, something had to come along and mess that up.
Meet the Menace: Hemlock Woolly Adelgid (HWA)
Native to Asia, the Hemlock Woolly Adelgid (pronounced “uh-DEL-jid”) hitched a ride from Japan and eventually showed up in Virginia sometime in the early 1950s. It looked around, saw all our lush hemlocks, and thought: “These trees have no idea what’s coming.” Asian hemlocks, which have adapted their defenses, are resistant to this little insect. Our Eastern Hemlocks? Not so much. It’s like putting a medieval knight into a UFC cage match. Spoiler: the knight doesn’t win.
This little menace is tiny—about the size of a period. Like, this → . You probably won’t notice the insect itself, but you will notice its calling card: little tufts of white fluff stuck to the undersides of hemlock needles. It’s not mold. It’s not snow. And no, your tree isn’t turning into a Q-tip.
That white fluff is a waxy, wool-like substance secreted by female adelgids. It’s their version of a minivan with tinted windows and car seats—basically a cozy protective shelter where they can raise hundreds of baby tree-killers in peace.
Why It’s a Problem
These insects feed on the tree by inserting their needle-like mouthparts at the base of the needles and sucking out nutrients. It’s kind of like a mosquito for trees! Over time, this feeding disrupts the tree’s ability to produce the sugars it needs. Needles fall off, new growth slows, and the tree becomes stressed and weakens. Sadly, the tree eventually succumbs to mother nature’s fate. As I write, my crew of arborists are currently removing several hemlocks who lost the fight.
Hemlocks don’t usually go down without a fight—but without intervention, they don’t stand much of a chance.
What Can You Do?
Inspect your hemlocks. Flip over some needles and look for white fuzz near the twig. It’s pretty easy to identify. Most hemlocks have some adelgid. A little is not a major cause for concern but it can get out of control.
Call an ISA certified arborist. They’ll know what to look for and how to treat it effectively. Be leery of those whose only tool is a chainsaw! For smaller trees there are several products containing imidacloprid that you can apply yourself. This can be ecologically dangerous so make sure you apply it only according to the label’s instructions.
Don’t panic. Okay, maybe panic a little. But mostly: act! Thankfully, this pest is relatively easy to manage in its early stages.
Save the Grandpas of the Forest
Our Eastern Hemlocks are ecological powerhouses. They cool streams for trout, shelter birds and wildlife, and make forests feel like enchanted fairytale groves. Let’s not let them go out because of something smaller than a freckle and fluffier than a lint ball.
If you’ve got hemlocks nearby, take a peek under those needles. And if you spot any of that mysterious fluff, get some expert eyes on it. Your trees—and future generations—will thank you.
Mike White is an ISA board certified master arborist and owner of Treemaster LLC. If you’re interested in learning more about tree related issues, you’ll find him to be moderately obsessed. You can reach him at mike@treemasterllc.com.
