What is dog-strangling vine? I don’t think I knew what it was about 6 years ago when I moved to my current home. Its twining choke-hold was already there; along the fence between my neighbour and I, sprouting up in the flower beds, and angrily attacking the little sun-dappled clearing behind my back yard. This vine would climb trees, shrubs, or even itself to wind together like stands in a rope to push itself higher and higher.
Then in mid-summer, the long bean-like pods began to appear. As these crack open in fall and winter, the wind carries the delicate gossamer seed wings far and wide. Dog-strangling vine (DSV) is more insidious – willing to stretch and spread by its voluminous seeds, but also its root system. If you break a root, it grows again. If you chop up a root, it will thank you by offering more plants.
So what can be done with this invasive species that is spreading each and every year to take over the grasslands, forest floors, meadows and alvars of Ontario?
Let’s look at what it really is. Dog-strangling vine is not a pretty name but a deserved one. It is strong, climbing, hard to break and hardy enough to choke out native species and block forest regeneration. It is a foreigner and significant ecological threat to our area… and is spreading wide from here to Rhode Island utilizing the ample fertile soil, sun, and lack of predators. This vine is swallowwart – from the periwinkle and milkweed family of the Ukraine. It is hardier and more adept at pushing out the local milkweed, which is the only nursery to monarch butterflies.
The only effective eradication method so far is to cover the area with a tarp and let it die down. Some efforts have been made to simply mow it in large areas. My own efforts have been to cut it at its base and let it starve for oxygen and photosynthesis. It will come back up at least once, but if I cut it again, it’s successful. At worst, it is too weak to create seed pods. But this is impossible to do across Altona Forest and Rouge National Park which have large areas rife with it. Across this whole area of North America, it seems a losing battle.
There may be a new hero on the near horizon. The caterpillar of the moth ‘hypena opulenta’ feeds exclusively on the invasive dog-strangling vine and is being tested in the field for release. Search for a safe biological control has been ongoing on both sides of the border for about a decade and 2013 saw it’s testing in the field and it’s approval for Canadian release. Now in 2014 there have been controlled release sites – this summer the little green caterpillars have been eating north of Toronto. Will a phased full-release be next?
What is more dangerous – the continuing and spreading destruction by dog-strangling vine, or releasing a new foreign insect into the region? What do you think?
Resources ~ Begin your reading here:
Dog Strangling Vine Fact Sheet – http://www.invasivespeciescentre.ca/SiteAssets/Files/Learn/Species/dog_strangling_vine.pdf
Bio-Control (U of T) – http://www.exchangemagazine.com/morningpost/2014/week32/Tuesday/14081214.htm
Hungry Caterpillar (U of T) – http://news.utoronto.ca/hungry-caterpillar-u-t-researchers-enlist-tiny-ally-fight-against-invasive-plant-species
Invasive Vines (Cornell) – http://www.news.cornell.edu/stories/2014/04/invasive-vines-swallow-new-yorks-natural-areas
Dog-strangling Vine (Ottawa Citizen) – http://ottawacitizen.com/news/local-news/the-tale-of-the-moth-and-the-dog-strangling-vine
Researchers Release Moths (U Rhode Island – 2013) – http://www.uri.edu/news/releases/?id=6791
Host Specificity of Hypena opulenta : A Potential Biological Control Agent of
Vincetoxicum in North America (Darthmouth – 2012) – http://www.dartmouth.edu/~asweed/Research/Publications_files/Hazlehurst-2012.pdf
Invasive Plants of Natural Habitats in Canada (Environment Canada) – https://www.ec.gc.ca/eee-ias/78D62AA2-55A4-4E2F-AA08-538E1051A893/invasives.pdf
Dog Strangling Vine: http://www.ofnc.ca/fletcher/invasives/swallowwort/index_e.php
Will Dog-Strangling Vine Meet It’s Nemesis? ~ © 2014 Natasha G