By Abby Bezrutczyk, LIISMA Field Project and Outreach Coordinator
—
Have you seen any hemlock trees recently?
Although New York State has the most hemlock trees in the US, eastern hemlock trees (Tsuga canadensis) tend to be a rather uncommon sight on Long Island, especially in natural areas. This local scarcity is partially due to development and habitat suitability, but more critically, because of a tiny aphid-like insect that’s been around for decades: hemlock woolly adelgid, or HWA (Adelges tsugae). While HWA has swept through the LIISMA region, we think there may be some resistant stands out there; the New York State Hemlock Initiative needs our help to locate these survivors.
Hemlock trees (not to be confused with poison hemlock of the carrot family), are a keystone species in the ecosystems they inhabit. That’s because they can grow in rocky slopes where they play an important role in stabilizing soil and preventing erosion. You know the instant you enter a hemlock-dominated forest: the heavy shade these trees provide is like someone turned off the lights. This feature can moderate air and water temperatures, and select for the species that live in their shade. Their great heights, soft-green undersides of their short needles, and marble-sized cones just add to their aesthetic appeal.
But hemlock woolly adelgid has been out to get these trees on Long Island since the 80’s, and it hasn’t stopped there, as Nicholas Dietschler of the NYS Hemlock Initiative (NYSHI) says, “HWA has devastated hemlock forest throughout much of the east coast and continues to spread northward.” In the fall, winter, and spring, these insects sap nutrients from the small twigs, sticking their mouthparts into the base of needles. Its characteristic white fluff builds up at the base of needles, protecting its eggs from winter temperatures. The wounds inflicted by the pest prevents further flow of nutrients, killing off new buds: years later, needle loss and fatality follows. HWA’s range of damage now extends to the Finger Lakes, Capital Region, and most recently, the Adirondack Park.
But there is something we, as the LIISMA community, can do. “Despite severe decline and mortality throughout much of eastern hemlocks range, including the Lower Hudson Valley and Long Island in NYS,” says Nick, “locating and protecting the remaining hemlocks is crucial in preserving ecological diversity.” We know there are still some out there – tucked away in parks and preserves, nestled in a private woodlot, or hidden in plain sight.
Once a hemlock tree is found with HWA, what can we do about it? “Tools for managing HWA and conserving hemlocks are numerous,” says Nick, “including targeted chemical treatments and biological control, providing hope for the future of hemlock in NYS and across its native range.” Helping the team find healthy hemlocks that may be exhibiting natural resistance to infestation is a crucial piece of the puzzle.
What’s more, Nick and colleagues at the NYSHI are working on such biological controls for hemlock woolly adelgid. Biological control is the use of a natural predator, parasitoid, or pathogen to manage populations of a pest species, and in this case, the team is researching predators of HWA from its native range of Japan to add an important tool for its management. This collaborative work is something to be excited about, as biological control is a potential tool to conserve hemlocks at a landscape-scale, in a way that other tools cannot.
So if you see hemlock trees on your hikes, bikes, or in your backyard– please let us know! You’re helping us preserve the genetic diversity of hemlock trees in our region. You can log hemlock trees and hemlock woolly adelgid in iNaturalist, or iMapInvasives. Thank you for being an active and integral part of the LIISMA community.
