Taking Care of Our Hemlocks

· Sangha News

Hemlock trees native to the Monastery region of the northeast have been greatly threatened by an invasive insect known as HWA (Hemlock Wooly Adelgid). Sangha members in the MRO Earth Initiative’s “citizen science” project have been assessing and monitoring HWA on the Monastery property this past year and offer this update on protecting our trees.

Once clear-cut from the mountain by the tanning industry, our remaining old growth and younger hemlocks have become infested with HWA. The US Forest Service says: “because of its dense evergreen foliage and dominance in riparian and cove habitats, eastern hemlock plays an important role in the area’s water cycle, regulating stream flow year round.” Informed by data and consultation with the NYS Hemlock Initiative, EI sangha concluded that the best and most effective way to save these beneficial trees on the property was to apply pesticides. The option to release bio controls—silver fly predator of HWA—was ruled out due to poor outcomes due to the cold at our elevation after a trial run at Overlook Mountain.

A healthy eastern hemlock branch

The Monastery hired Healthy Trees Inc. in the spring to spray twenty-seven mature hemlock trees on our property in an attempt to combat the HWA infestation. Healthy Trees used a combination of two different chemicals, imidacloprid and dinotefuran, which have been shown to be very effective. The application method used for the treatment was a basal bark spray from which the insecticides are taken up by the vascular system of the tree and eventually will be present in all the foliage, protecting them from HWA. For more information:

When insecticides are used judiciously they are very effective at combating HWA. They are also effective against Hemlock Elongate Scale insects, another infestation of hemlocks in the eastern US and here in Mount Tremper. The benefits of using these insecticides far outweighed the risks and that we need to protect these ecologically necessary and irreplaceable trees, according to Shugen Roshi. We originally planned to spray up to 100 trees but decided to start with a smaller number with an eye on potentially spraying more in the future. The Earth Initiative will continue its citizen science work to monitor the presence of HWA.

Mature eastern hemlock forest

The EI sangha are grateful for the advising, guidance and dedication of the NYS Hemlock Initiative staff, and for Vern Rist, the owner and operator of Healthy Trees LLC, who has advised and helped the Monastery care for its forests for many years.

HWA Earth Initiative monitors: Sansho Benton, Eisho Meyer-Emerick, Jusan Chen, Hosui Vasan, Nyuko Schadnow and Taikyo Gilman.

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