Tim Toman, WV State Entomologist, prepares a tree for a stem injection.
Photo by Ellen Hrabovsky.
HWA at base of hemlock needles.
Photo by Ellen Hrabovsky.
Hemlocks add ecological importance and beauty to our forest trails.
Photo by Erin Smaldone.
The days of many hemlocks (Tsuga Canadensis) may be numbered but not all! We have a gorgeous forest at the WV Botanic Garden and our hemlocks are the crown jewels of that forest. Thanks to the efforts of many researchers with the USDA Forest Service and the WV Department of Agriculture much has been done to further the possibilities of their survival.
Why do we care about hemlocks? Their dense canopy shades and cools streams providing a very good aquatic habitat; they protect against erosion; the deep duff layer retains moisture and they provide an excellent wildlife refuge. They are lovely ornamentals and in some places, because they are so long-lived they have great historic significance.
The Hemlock Woolly Adelgid (HWA) (Adelgis tsugae) was imported accidentally from Japan and was first recognized in Richmond, Virginia in 1950. In the 1990’s it exploded on the scene throughout the Eastern United States, devastating the forests of New Jersey,
Virginia and other areas east of the mountains. It rapidly made its way over the mountains and is found throughout West Virginia. Luckily, it was not spotted in the West Virginia Botanic Garden (WVBG) until 2012 and treatment was quickly initiated.
Our criteria for treatment include healthy trees within 1 ½ tree lengths of our hiking trails and trees of ecologic importance such as shading streams and providing dense habitat in our forests. Hemlocks within some special gardens were included. Small trees as well as large, old beauties were treated. In all 620 trees on the east side of the reservoir basin were measured, marked and treated with an insecticide in 2012- 2013. An additional 50 trees were treated in other sensitive areas of the garden. Trees within 15 meters of streams received an injection into the tree to avoid contamination of waterways.
Another treatment option is the use of biologic controls. In Asia there are several beetles that feed only on the adelgid. Many of these have been extensively studied, quarantined and then released in an attempt to slow down the ravages of this invasive insect. A formal release of biologics has not been done at the WVBG. Our hemlocks remain healthy and we are sure that the recurring visits of a polar vortex help. The adelgid is not acclimated to very low temperatures.
Working with the team from the WV Dept. of Agriculture Plant Industries group we have been inspired by their dedication and their love of our forest, particularly our hemlocks. Comments such as “This is the new Cathedral…” and “This is what a forest should look like” should inspire us to continue to protect our forests.
by Dr. Ellen Hrabovsky, Guest Contributor
Originally published in our Spring 2020 newsletter