One university's fight against invasive species

Grossman Pond at Cornell Plantations
CC BY-SA 2.0 John Menard

How Cornell University is protecting its nature preserves from the threat of invasive plants and animals.

Cornell University in Ithaca, New York is home to one of the state’s largest and most prominent botanical gardens, the Cornell Plantations. Created in the mid-19th century as a part of the university’s dedication to the natural sciences, the Plantations consists of a 100-acre arboretum, 25 acres of gardens, and over 4,000 acres of nature preserves.

Unfortunately, an influx of invasive species has put many of the Plantations’ over 40 natural areas in jeopardy. Newly introduced non-indigenous species can compete with and consume native plants and animals, dramatically reducing biodiversity in the Plantations. Invasive insects are especially dangerous, as their consumption of native plants could potentially lead to the extinction of trees and flowers that have been housed at the Plantations for over a century.

The hemlock woolly adelgid (Adelges tsugae), or HWA, poses one of the most serious threats to the ecosystems of the nature preserves. HWAs are Japanese insects that feed on the sap of young hemlocks, destroying the trees’ needles and branches and eventually killing them. The insect was first found in the Plantations in 2009 feeding on eastern hemlocks (Tsuga Canadensis), trees that are integral to the Plantations’ many wooded areas. Eastern hemlocks provide cool, shaded habitats for plants and animals across New York state and cover over 700 acres of land on the Plantations. If left untreated, a hemlock infested with HWAs has a mortality rate of nearly 100%.

Hemlock woolly adelgids on a branch© Mark Whitmore

Todd Bittner, the Director of Natural Areas at the Plantations, is fighting back. Along with a staff of gardeners and researchers, Bittner has already treated over 2,500 hemlock trees with insecticide in hopes of protecting them against the adelgid.

“The impact of losing our hemlocks is so significant because they are such an important part of the forest ecosystem,” Bittner told TreeHugger. “We want to control [the hemlock woolly adelgid] but eradicating it is not a viable option. We went about a process of prioritizing the hemlock lands for protection, taking into account their proximity to campus, their iconic nature around our lakes and gorges, and their value to academic class use and research.”

So far, Bittner’s team has treated hemlocks in about half of the Plantations’ 17 infested natural areas by injecting insecticide into the trees' trunks or into the soil, but this process is time consuming and expensive. Researchers at Cornell and other universities hope to develop biocontrol agents that can more efficiently combat the insect. In 2009, Mark Whitmore, a Cornell professor, helped to introduce the Laricobius nigrinus beetle, which feeds on the adelgid, into the Plantations' forests as part of 10 year study on HWA biocontrols.

Hemlock being treated for HWAs© Cornell Plantations

To reduce the introduction of invasive species into the Plantations’ gardens and natural areas, the staff has also developed an Invasive Species Code of Conduct based on similar codes used by many other botanical gardens. The Code of Conduct highlights the species that pose the biggest threats to biodiversity and explains risk assessment and evaluation protocols. It also forbids the use of invasive plants in the Plantations’ cultivated collections, a policy that Bittner praises.

“Many invasive plants were introduced for horticultural interest and have subsequently escaped,” Bittner noted. “We want to minimize the possibility of that happening over and over again.”

Bittner hopes to use the invaders that have already become established in the Plantations as examples to educate the public about the dangers of invasive species. He and his staff utilize invasive trees that are difficult to manage, such as the Norway maple (Acer platanoides), in public demonstrations to highlight the difficulty of removing invaders once they have become established.

“Once an invasive species establishes in an environment, it is extraordinarily difficult and expensive to control them,” Bittner explained. “In the long run, the most cost effective means of control is for us as a society to prevent the introduction of invasives in the first place.”

To learn more about the Cornell Plantations and their fight against invasive species, visit their website at

Tags: Invasive species | Nature | New York State


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