3 September 2007

DSV control - the High Park experience

Nobody I know likes pesticides or enjoys working with them, but, they have their place.

Honestly, I see glyphosate as a treatment for DSV invasion a lot like I see chemotherapy as a treatment for cancer.

When my mother was diagnosed with cancer, the oncologist told us (and, forgive me, but what he said still reminds me of weed eradication protocols): "our methods are still crude: we can cut it (surgical oncology), burn it (radiation) and poison it (chemotherapy)." Suddenly something as previously unintuitive and horrifying, as having my mother subjected to courses of poisonous chemicals, had become a hopeful option (in a new reality
with nothing but compromised options and outcomes) that might prolong or save her life. An option and a pressing decision too.

High Park includes globally rare Black Oak Savannah remnants. The folks who steward that site have a local and international responsibility to preserve the indigenous flora and fauna there = High Park is an excellent example of when glyphosate is an excellent choice (again, in a new reality with nothing but compromised options and outcomes) for conservation.

Restoration Challenges: The Ongoing Battle with Dog-strangling Vine Control at High Park

By Cara Webster

The City of Toronto established a restoration crew dedicated to the restoration of the Black Oak savannah and woodland habitats in High Park in 2000. The project is now in its fourth field season and has made many successes to date with the control of invasive plants, the reintroduction of fire and the reintroduction of native plants. One very persistent invasive species, Dog-strangling Vine (Vincetoxicum rossicum and V. nigrum) has presented many challenges to the restoration of High Park. Dog-strangling Vine is a perennial herbaceous vine that easily invades the open habitat of the savannah and it also tolerates some shade in the woodland areas. Once Dog-strangling Vine is established it produces an extensive root system and abundant seed that is easily spread into adjacent areas. Volunteers in High Park attempted to control Dog-strangling Vine with manual methods such as cutting and pulling but had little success. The reintroduction of fire has also been unsuccessful at controlling this species and it may in fact be giving it an advantage early in the season. Test plots were set-up before the spring burn this year to observe differences in emergence, density and other factors between burned and unburned plots. We will continue to monitor these plots to observe long-term effects. Due to the lack of control using other methods the restoration crew has been using intensive treatments of herbicide over the past three years.

Chemical Control Methods of Dog-strangling Vine
Several different methods of herbicide application, herbicide types and dilutions have been tested to develop an effective control for this species. Roundup-Transorb, a glyphosate based herbicide, is being used since its formulation allows quick absorption and is very practical in the field since it can be applied up to an hour before rainfall. A 33% dilution of Roundup-Transorb is applied to plants using a car wash mitt to wick the plants and avoid harm to the surrounding native vegetation. Large monocultural stands are sprayed using a backpack sprayer or hand sprayer. We have found that the label recommended 2% dilution to be used in a sprayer is not very effective at controlling this species but we are continuing to track these results. Treatments have been initiated each year at the beginning of June and continue until early September to cover approximately 20 hectares in High Park. Each area is treated twice over the field season, spaced at least one month apart, to re-treat persistent plants and to catch the next plants coming into flower. Many large colonies in the park have been reduced, however, longterm maintenance is required to prevent re-establishment by individual stems. In 2002 and 2003 an additional crew has also been contracted to cover a larger area of the park and to prevent seed in untreated areas from spreading into treated areas. Priority is given to areas with rare species and areas that will be burned the following spring to prevent further encouragement of Dogstrangling Vine. Although it has been a labour-intensive process the Dog-strangling Vine population at High Park is being reduced. Three former Dog-strangling Vine colonies have been re-planted with native species to recapture the bare sites. Some colonies in the woodland areas have been able to naturally regenerate with plants from the surrounding area and from the seed bank. The restoration crew will continue to monitor the results of these efforts and develop new strategies to protect the rare Black Oak savannah.

For further information, or if you have any other experiences to share, please contact cwebster@toronto.ca.
Cara Webster is Restoration Specialist with Urban Forestry Services for the City of Toronto.

From: http://www.serontario.org/pdfs/jul2003.pdf


1 comment:

Emma Rooney said...

With the updated information you have provided on DSV, I have had it on my mind a lot lately and I really think we need to start educating everyone around us (even if they aren't avid gardeners or environmentalists) because managing the DSV is a task too big to tackle alone.
I've written today on my blog a few reflections on the topic! Thanks for your efforts in public education.

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