LAWRENCE, Kansas – April 5, 2016 – Scientists have just concluded a six-year study of potential controls for pale swallowwort and black swallowwort (Vincetoxicum spp.) – two perennial vines native to Europe that are invading habitats in northeastern North America.
To date, broad-spectrum herbicides have proved to be the most effective tool for managing the swallowworts. Many land managers, though, are concerned about the expense of herbicide treatments and the potential impact on native plant species in the areas being treated.
Researchers from Cornell University and the USDA Agricultural Research Service set out to determine whether defoliating swallowwort vines or mowing them would impact the growth, reproduction and survival of mature plants.
Researchers knew a long-term study would be needed to better predict results for a perennial plant like swallowwort. Their field experiments on the Cornell University campus documented six seasons of treatments of varying intensity.
They artificially defoliated swallowwort vines by 50 percent or 100 percent once or twice a year to simulate the impact of a leaf-feeding biological control agent. They also clipped vines once, twice or four times a year to simulate mowing.
In an article featured in the most recent edition of the journal Invasive Plant Science and Management, researchers say none of the swallowwort plants died as a result of defoliation or clipping, even at maximum treatment levels. Black swallowwort produced more above-ground biomass, while pale swallowwort produced more root biomass and root crown buds, compared to the other species. Clipping four times per season did eliminate swallowwort seed, but it didn’t destroy mature plants. Plants receiving other damage treatments continued to produce seed and increase in size.
“The lack of success using defoliation and mowing over a multiyear period means land managers will likely need to continue to use herbicides in order to fight swallowwort infestations effectively,” says Lindsey Milbrath, Ph.D., of the USDA Agricultural Research Service, lead researcher for the project.
Full text of the article “Tolerance of Swallowworts (Vincetoxicum spp.) to Multiple Years of Artificial Defoliation and Clipping” is available in Volume 9, Issue 1 of the journal Invasive Plant Science and Management.
About Invasive Plant Science and Management
Invasive Plant Science and Management is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication focuses on invasive plant species. To learn more, visit www.wssa.net.