Our Hemlocks are Dying

by Randy Weidner

The Hemlock Wooly Adelgid is an invasive insect from Asia attacking hemlock trees. This forest pest has been active in Mossy Bank Park for about 10 years. The natural course of this infestation leads to the death of hemlock trees in about 10-20 years.

There are effective but expensive insecticidal controls for individual trees, but this is impractical for a forest. The hemlocks within the drive-around in the park have been treated, but reapplication is necessary every 6-7 years.

For several years we have been co-operating with the New York Hemlock Initiative, a joint project of Cornell University and NYDEC, including serving as a site for release of introduced potential control insects (silver fly). These efforts have so far failed as controls.

One management choice is to let nature take its course. As trees die, we will cut only those that pose a hazard to roads and trails. Regrowth of new trees would come from the soil bank of tree seeds.

However, deer will likely browse regrowing hardwoods, causing them to be short and stubby, potentially preventing these young trees from reaching full growth. There is further risk that non-native invasive shrubs could move in, overwhelming the trees we wish to promote. Without controlling deer and invasive shrubs, it is unlikely a desirable new forest will regrow, diminishing the long-term aesthetics of the park.

Another management choice is to cut the hemlocks from areas well suited for using the downed trees to construct barriers called slash walls. The goal of this approach is to keep deer out and better allow new trees to grow.

Any intervention, or lack thereof, will result in a change in the nature of the present forest, and a new forest will take a long time to regrow. Constructing slash walls has been tried in other areas of upstate New York and shows promise for allowing regrowth of healthy new forests where it has been done.

In early 2022, the Mossy Bank Park committee engaged the services of forestry experts for advice. All agreed that the forest, as it now exists, will disappear; and that we might expect to regrow a desirable native hardwood forest in certain specified areas by removing all of the hemlocks but a few legacy trees, leaving selected hardwoods, and using the logging debris to build slash walls. The total area impacted by this operation will be slightly less than 1/3 of the total park area, and will not include any of the heavily used park facilities or areas visible from the drive-around.

A plan to remove selected dense hemlock stands and build slash walls was approved by the Mossy Bank Park Committee and the Village Board of Trustees. An appropriate contractor versed in this type of management has been located, and this plan will be implemented in the near future.

Picture of Hemlock Wooly Adelgid

Hemlock Wooly Adelgid Infestation

Dead Hemlock Trees
Dead Hemlock Trees from Wooly Adelgid
Licensed Sprayer
Certified Licensed Sprayer
Silver Fly
Silver Fly, very tiny
Deer browsing
Deer browse on young trees, stunting them.
Autumn Olive
Invasive species such as Autumn Olive and Multiflora Rose can move into space left by dead trees.
Multiflora Rose
Slash Wall
Slash Wall
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