Visitors to the Great Smoky Mountains have been captivated by the scene for decades: gorgeous evergreen trees clustered around the rushing waters of boulder-strewn mountain streams. The trees, in most cases, are hemlocks, their roots snaking impossibly among the lichen-covered rocks and their needle-laden branches framing the streams in postcard perfection. In winter snow, with powder piled deep on both boughs and boulders, the scenes can be breath-taking.
Unfortunately, hemlocks are in very real danger of being wiped out. In the past few decades a tiny insect called the “hemlock wooly adelgid” has spread like wildfire from New England to the Carolinas and on into the Georgia mountains, leaving experts worried the trees will go the way of the American chestnut and the Dutch elm. As you might guess, the hemlock tormentors were imported from overseas by humans, coming from Asia, unintentionally, I’m sure.
You can spot an infested tree in a second: just turn over a low branch or look up to the underside of one higher. The adelgids, which are themselves almost too tiny to see with the naked eye, create small white cottony tufts that start out as dots but can grow so thick they almost carpet the bottom of the branches. You’ll recognize them immediately and the tree will probably look “sick:” wan, with spotty needles of a weak, grayish green instead of a vibrant, greenish-blue. There are bare, dead branches in advanced cases. The insects sap the life from the trees and quickly send them on a downward spiral that can kill a healthy 80-footer within a few years.
Biologists are studying the problem but as yet there is no great hope for a reversal of what appears to be a possible march toward extinction. They are experimenting with a species of beetle (a non-native, unfortunately) that feasts on the adelgids, but this has not yet proven to be a large-scale solution. It also seems like typical human tinkering, messing around with a web of life far too complicated for us to completely understand, that may well turn out to have unintended consequences and could wreak havoc on some other part of the eco-system. A biologist I ran into on a hike was collecting samples of infested hemlocks; she warned me, as an individual property owner, away from the beetles, saying they were best left for now to researchers and experts.
But there is another human solution: an insecticide. It works, but it is costly, difficult to apply and carries plenty of its own hazards, as it kills more than just adelgids. To me, it’s akin to the “nuclear option.”
Nevertheless, my wife and I pondered long and hard about whether to use it on our hemlocks in North Carolina. We love the trees dearly, and I can’t bear to stand by idly and watch them die. We finally decided we had no choice, because if we did not use it, it was clear we would lose every last one of our several hundred hemlocks. Many were infested when we bought our land, and several were near death.
The treatment is sweaty, hard work, filled with slippery climbs up steep slopes, slashing briars and branches poking you in the eyes. You inject the insecticide around the tree’s roots with a hand-pumped gizmo with a big needle on the end that is jabbed into the ground. It’s especially difficult work in rocky soil. A second method is to instead splash the poison around the base of the tree, something that doesn’t work too well on a steep slope. With both methods you have to make repeated trips to fetch water for your mix or to refill the injector, and the water for the injector must be free of all debris or the device will clog.
A third application method is to spray, an option only practical for baby trees, while a fourth is a system that requires drilling holes in the trunk and injecting the poison directly into the tree. This last method is very slow, cumbersome and the equipment quite expensive, but it’s safe for the surrounding environment and is the only option if the tree’s “feet” are near a stream, which you don’t want to pollute with poison injected into the ground.
I have tried all four methods and they are effective. While I continue to feel uneasy using high-powered chemicals, so far I have seen no ill-effects on other plants or bugs, although I’m sure the poison must be killing more than just the adelgids.
Yet another problem with the poison, though, is that it wears off after a few years and the trees must be treated again or they will be re-infested and eventually die.
So property owners who love hemlocks face tough choices: either watch your trees die, hire a tree service that will no doubt charge steep prices, or do the work yourself. The injector costs about $300; the cost of the insecticide is tough to estimate, but my best guess is that it runs something like $10 to $15 for a large tree, about 25 inches in diameter.
The biologist I met did give me a small reason for optimism. She said researchers have found the adelgid population itself often eventually crashes, at least locally, because the bugs kill all the hemlocks and must move on to fresh territory to survive. That gives me hope that the wave of bugs currently infesting our valley may one day retreat and I will find our hemlocks no longer need the poison to live. But it may well be that by keeping our trees healthy I’m keeping the adelgids around.
For all the cost, difficult work and worries over injection poison into soil, though, it is immensely gratifying to see our hemlocks thriving. The trees on many adjoining properties are untreated and are well on their way to dying, making a painful scene. But most of ours are flush with life, sprouting tips of bright green new growth, the limbs lush with healthy needles. I sometimes talk to them when I visit, urging them on, promising to do everything I can to help.
Some state and national parks, including the Smokies, have begun treating some of their infested hemlocks, too, although they can afford to do so only on small clumps of trees in high-visibility areas. The trees in the deep woods, miles from any road access, are most likely doomed. And even the accessible ones are typically nestled beside rushing mountain streams, meaning the only way to save them is the direct injection method, the most costly, cumbersome and time-consuming option.
Some hemlocks will likely survive, either by natural selection, luck or the persistence of the owner of the ground on which they stand. But the outlook is not good. In all likelihood, those heart-warming views of hemlocks, boulders and rushing water – views that for many are the unforgettable part of a visit to the Smokies – may be numbered.
For more info on hemlocks: www.saveourhemlocks.org.
To make a donation: www.friendsofthesmokies.org. This group has donated more than $1 million to save hemlocks in the Smokies.
Top photo: A hemlock that has been treated and is healthy
Middle photo: The hemlock wooly adelgid (larger than actual size)
Bottom photo: Adelgids infesting a hemlock branch