Cornell Botanic Gardens receives grant to conserve, research hemlock

A Cornell Botanic Garden employee inoculates a hemlock tree against hemlock woolly adelgid, while hovering over a gorge.

Cornell Botanic Gardens has received a grant from the New York State Department of Environmental Conservation to continue and expand its work to conserve hemlock trees that are foundational to the university’s campus and natural areas. The Invasive Species Rapid Response and Control grant will be used over three years to control hemlock woolly adelgid, an invasive aphid-like insect wiping out hemlock populations across eastern forests.

Ecologists refer to hemlocks as a “foundation species” for the plant communities in which they grow because the trees have a profound influence on the survival of other organisms.

“Hemlocks promote a cool, moist environment near gorges and stream corridors that many other species require,” said Todd Bittner, Cornell Botanic Gardens’ director of natural areas. “Without these conditions, plant and animal diversity is diminished, ground and water temperatures increase, and stream flow changes, putting species and habitats at risk. There is more to lose than just hemlocks.”

To control the invasive pest and conserve hemlock stands, insecticides are administered in single-tree treatment through trunk injections or bark applications. Since 2009, Cornell Botanic Gardens has treated and saved 3,000 hemlock trees around Beebe Lake, Cascadilla and Fall Creek gorges, and other important natural areas on and off campus. The pesticides translocate to the growing branches where the adelgids feed, and the treatment remains effective for seven or more years.

With the support of the $68,723 grant, 1,200 previously treated and additional trees will be treated. The grant also funds efforts to identify new hemlock woolly adelgid infestations and to research the effectiveness of biocontrol agents. The latter is in collaboration with Cornell forest entomologist Mark Whitmore, extension associate in the Department of Natural Resources in the College of Agriculture and Life Sciences. Whitmore studies the release biocontrol agents as a forestwide treatment and prevention method for controlling hemlock woolly adelgid.

Whitmore has been developing biological control agents that keep the hemlock woolly adelgid population in check. Three insects, Laricobius nigrinus, Leucopis piniperda and Leucopis argenticollis, originate from the Pacific Northwest and are expected to work in concert with one another as predators of the adelgids. The latter two species, both silver flies, will be released and tested in Cornell Botanic Gardens’ hemlock forests in spring 2018.

In another collaborative effort with Whitmore, Cornell Botanic Gardens is caring for about 40 introduced hemlock trees, sourced from a potentially adelgid-resistant stand discovered about 12 years ago in New Jersey. Whitmore and other researchers are attempting to discern if the apparent resistance is due to a unique hemlock adaptation or conditions present in the trees’ original location.

Conserving hemlocks, an iconic species in Northeast forests, is a concern shared across government, conservation and research organizations, and the public. Without intervention, hemlock woolly adelgid will continue to spread and forever alter hemlock forests and the species they support. Cornell Botanic Gardens is working with conservation partners and the public to address the threat to forests from the invasive pest.

“Quickly identifying emerging populations is a key strategy in implementing any rapid response invasive control program,” Bittner said.

The public can play a vital role in helping land managers know about new hemlock wooly adelgid populations, and track its spread, by learning what to look for and reporting positive and negative sightings via Cornell Botanic Gardens’ website.

“We are at the beginning of a long road,” said Whitmore. “There is more research that needs to be done, but I am hopeful for the hemlock forests.”

Diana Buckley is a communications and marketing intern at Cornell Botanic Gardens.

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