Quietly infiltrating the great expanse of forests throughout New York State, invasive pest species continue to wreak havoc on countless ecologically and economically valuable trees. We’ve all learned about the devastating impact of Dutch elm disease and how the blight that made the American chestnut (once the most common tree in our eastern forests) go functionally extinct. More recently, beech blight and emerald ash borer have killed untold numbers of trees in our area. Over the past century these pests have significantly altered the species composition of our forests. And there’s more to come.
Beyond their commercial impacts, the cumulative damage caused by these new harmful invasives is slowly but surely undermining the health and resilience of our entire ecosystem. Like a real-life game of “Jenga,” the extinction or significant reduction of tree species after tree species is leaving our forests increasingly at risk of ecosystem collapse. Their disappearance doesn’t just impact the trees themselves – the damage extends to all other species that depend on them as well.
For many years, the Chautauqua Watershed Conservancy, other area organizations, and many dedicated citizen scientist volunteers have been carrying out pre-emptive surveys for Hemlock Woolly Adelgid (HWA). HWA is an aphid-like insect that threatens the health of the eastern hemlock (Tsuga canadensis) throughout the eastern United States. This exotic invasive insect pest is spreading further north and east from its introduction point in Virginia in the 1950s, infesting and causing decline and mortality in ecologically significant hemlock-dominated forests. Based on our surveys, we know that HWA has been present in our area for many years, but until recently, it was limited to only a few sites that were carefully monitored and, where possible, treated. Unfortunately, throughout 2024 we have received and confirmed many new outbreaks of HWA across Chautauqua County, and it appears that HWA is suddenly becoming a real threat to yet another key component of our beautiful forests.
What makes HWA potentially even more impactful than other forest pests is that hemlocks tend to grow in large, single species stands. Being evergreens, hemlocks form dense clusters that don’t allow much light to reach the forest floor year-round. Areas with significant hemlock growth therefore tend to have very little undergrowth because young tree saplings can’t grow in these low light conditions. As a result, once HWA moves in and hemlocks die, entire hillsides and large sections of forest can rapidly be left completely devoid of trees. An added challenge is that hemlock stands tend to cover and stabilize steep slopes above streams and rivers. Losing all tree cover from such areas in a short period of time can lead to erosion, landslides, and significant impact on water quality in the streams below – something that has been happening for some time now in the Catskills, the Blue Ridge and Smoky Mountains, and many other places east and south of us.
Fortunately, there are some glimmers of hope. It’s likely that the recent string of mild winters has allowed HWA to propagate and spread. Even though HWA is suddenly spreading throughout our county, the cold weather we are experiencing this year may kill off some of these bugs. Also, significant strides have been made in recent years with new biological control methods, and field trials in the Allegheny National Forest and in Central NY seem to have promising initial results. Chemical control options are also available in the form of oils, soaps, or toxins that can be used to treat small HWA infections. However, such control methods are costly, need periodic re-application, and are not feasible for large infestations.
Most importantly for Chautauqua County right now is that we continue and expand our HWA monitoring efforts to have the most accurate distribution information available. That will help to ensure that infected areas are on everyone’s radar and informed management decisions can be made accordingly. It will also help us identify areas where trees appear more resilient – information that may help isolate genetic strains of hemlocks that could potentially withstand an infection. Winter is the best time to look for the presence of HWA because the overwintering bugs are immobilized in small, cotton ball-like capsules at the base of each hemlock needle, which makes them easy to detect. In addition, since the bugs are inactive during the winter, there is no risk that well-meaning surveyors inadvertently spread these pests to other hemlocks, simply by touching or brushing against infected trees.
Our forests need your help! We have several HWA surveys taking place in January, February, and March – some of which are open to the public. Please consider joining one! You’ll learn everything you need to know to recognize HWA and infected trees, you’ll learn about potential treatments, and you’ll be able to take that knowledge elsewhere – for example, to check on the hemlocks in your own backyard. And, not unimportantly, you’ll also get to enjoy a beautiful walk in the woods on one of our nature preserves or other forested area!
For more info about HWA or our upcoming surveys, contact our land specialist, Bethany O’Hagan, at bethany@chautauquawatershed.org. For a list of surveys that you can volunteer at, visit our Events page.
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