Pale and black swallow-wort are rapidly invading fields and forests across the Northeast, including New York, but a moth from the Ukraine holds promise to keep the weed in check.
The larvae of Hypena opulenta feed exclusively on the leaves of pale and black swallow-wort, and after years of research to verify H. opulenta’s safety to ecosystems, the moth was approved for field release by the U.S. Department of Agriculture in August 2017.
Now, just in time for New York Invasive Species Awareness Week, July 9-14, a team of botanists and entomologists has released the moths into research field cages at Great Gully Nature Preserve in Union Springs and at the Cornell University Agricultural Experiment Station’s Musgrave Research Farm in Aurora.
In the lab, H. opulenta larvae successfully fed on both pale and black swallow-wort. The field trial will allow the team to study how the larvae survive and establish themselves in natural conditions.
“It’s a lot of work, but once you get the right biological control agent out there, it can be one of the few solutions that is long-term and economical and sustainable,” said Carrie Brown-Lima, director of the New York Invasive Species Research Institute.
Like the moth, pale swallow-wort originates in the Ukraine, while black swallow-wort is native to the Mediterranean region of Europe.
Both species were likely introduced to the U.S. in the 1800s. With no North American natural enemies, these climbing vines threaten plant and animal habitats, including rare plant communities such as New York’s limestone alvar areas on the eastern shore of Lake Ontario.
Endangered species like Harts tongue fern found in Clark Reservation State Park near Syracuse are threatened by the vine. They also out-compete milkweed, a native relative of swallow-wort, where monarch butterflies lay their eggs and their larvae feed. When the vines grow in hay fields, they can get mixed with hay and may sicken livestock.
Later this summer, the team will release more moths into experimental cages at Green Lakes State Park in Fayetteville and at Robert G. Wehle State Park in Henderson. Additionally, University of Rhode Island collaborators are doing similar caged releases in other Northeastern states.
In addition to the USDA-ARS and NYS DEC, future work will be funded by Smith Lever Funds administered by the Cornell University Agricultural Experiment Station and the New York Department of Transportation.