Dog Strangling Vine - An Invasive Species Creeping Into Agricultural Fields

Dog Strangling Vine is an extremely aggressive plant species from the milkweed family that has traditionally inhabited field borders, roadside and rail tracks. More recently it has been creeping into agricultural fields and pasture lands across Ontario, but mainly east of Toronto (see Figure 1). To minimize the impact of Dog Strangling Vine in these areas it is important to understand how this plant reproduces so that control measures are effective as possible. 

General Description

Dog Strangling Vine is a perennial with a horizontal woody rootstalk or rhizome (Figure 2). The stems can range in length from 60 to 200 cm (24 – 80 inches) with a twining or scrambling configuration, hence giving it the “strangling” moniker. The leaves are ovate (oval) in shape, have smooth margins, with hairs being present on the margins and major leaf veins on the underside of the leaf (Figure 3). According to DiTommaso et al. 2005, the flowers of Dog Strangling Vine are a pink, red-brown or maroon, while “Black” Dog Strangling Vine has flowers that are dark purple to blackish. Flowers will produce pods containing seed that is similar in appearance to common milkweed. 

General Reproduction and Biology

Dog Strangling Vine can reproduce by seed and by its massive underground root system (rhizomes). The seed is extremely viable once it germinates and the rhizomes can also propagate many new plants. An example of this was illustrated in a growth room experiment conducted at the Department of Plant Agriculture, University of Guelph. Every time a rhizome section was cut, two new plants would arise from each severed end. 

In one season the vine has been known to grow as much as 1 to 2 m in size. Flowering generally begins in late-May and ends around mid-July. The fruit pods release seed from mid-August to early-November.

Control Options: Non-Chemical

The following is a summary of non-chemical control strategies that have been tested by Dr. Naomi Cappuccino, an assistant professor in the Department of Biology at Carleton University.  

Table 1. Non-chemical control strategies for managing Dog Strangling Vine.

Method	Strategy	Notes
Periodic Mowing	Stops the plants from flowering and thereby reducing seed production.	Doesn’t kill the plants as new ones will sprout up from the buds at the base of the stem.
Digging up roots	Remove the entire root of each individual plant.	Effective, but time consuming.
Mowing and Mulching	Mow the plants to stop seed production then cover area with a competitive mulch to stop sprouting of new plants from rhizome	Effective, but unsightly.

Control Options: Chemical

After a thorough literature search, only one herbicide label (Arsenal) lists Dog Strangling Vine as a species that will be controlled. There are a number of other products that have been tested and the results are shown in Table 2. 

Table 2. Notes on Herbicides that have been tested for the control of Dog Strangling Vine.

Product	Comments
Arsenal (imazapyr)	Dog Strangling Vine listed on label. Non-Crop Land Herbicide that is non-selective and has residual properties. Registered for use on “Clearfield” crops in the United States. Plant-back restrictions for other crops unknown in Ontari
Garlon 4 (triclopyr - 1% solution)	Source: http://tncweeds.ucdavis.edu/ Dog Strangling Vine not listed on product label. Can be used on grass pasture – re-grazing restrictions exist. Plant-back restrictions for other crops unknown in Ontario. U.S. data would suggest that corn, soybeans and wheat could be planted 2 weeks after an application of Garlon 4
glyphosate	A lot of variability in results presented in the literature. Growth room studies showed little activity (U of G, 2005). Leaf defoliation often observed, but control not achieved. 2% solutions are often recommended with timings to be made at the flowering stage for the most effective results.
Classic (chlorimuron)	Growth room studies showed little activity (U of G, 2005)
Dichlorprop/2,4-D	Growth room studies showed little activity (U of G, 2005)

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Do you have Dog Strangling Vine?

If you are interested in evaluating some of the above control options, please call me at 519-824-4120 ext. 52580. 

Figure 1. Distribution of Dog Strangling Vine in Ontario (Source: DiTommaso et al, 2005)

Figure 2. Cross Section through the woody rootstalk of Dog Strangling Vine (Source: DiTommaso et al, 2005)

Figure 3. Seedling of Dog Strangling Vine two weeks after emergence in a greenhouse (Source: DiTommaso et al, 2005)

References:

• The Biology of Invasive Alien Plants in Canada. 2. Cynanchum rossicum (Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] and Cynanchum louiseae (L.) Kartesz & Gandhi [= Vincetoxicum nigrum (L.) Moench]
• Antonio DiTommaso, Frances M. Lawlor, and Stephen J. Darbyshire, Can. J. Plant Sci. 85: 243-263

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