In numerous urban forest settings and isolated patches of rural forestland, English ivy (Hedera helix) persists as either groundcover or aerial vines (different life stages) attached and extending up into the canopy of trees. For some landowners, this plant is a nuisance and can hinder tree growth/development. This article will discuss research observations from current herbicide research (late winter basal bark application) being conducted to control English ivy within the Clemson Experimental Forest. Recommended chemical methods (including foliar applications, cut stump, and stem injection) to deaden the species will also be presented.
Clemson Forest Research
A small infestation (~1+ acres in size) of English ivy vines within the experimental forest was utilized to evaluate the effectiveness of the herbicides: aminopyralid (Milestone®) and triclopyr – pyridinyloxyacetic acid formulation (Trycera®) as limited literature exists on these two products’ effectiveness on English ivy. The carrier solution in which the herbicides were mixed was also investigated to determine if commercial diesel, methylated seed oil (MSO), or forestry basal oil would individually perform optimally. The addition of a penetrant adjuvant (Cide-Kick2®) to a couple of individual treatments (one for each herbicide) was also tested and evaluated.
1) 2.5% Milestone® + 10% Cide-Kick2® + 87.5% MSO (methylated seed oil)
2) 5% Milestone® + 95% MSO
3) 21% Trycera® + 79% MSO
4) 30% Trycera® + 70% MSO
5) 20% Trycera® + 10% Cide-Kick2® + 70% diesel
6) 30% Trycera® + 70% basal oil
7) 5% Milestone® + 95% diesel
*Milestone® = 21.1% aminopyralid – 2 lbs/gal (a.i.)
Trycera® = 29.4% triclopyr (acid) – 2.87 lbs/gal
Cide-kick II = d’limonene, related isomers, emulsifiers (wetting agent, sticker, activator, and penetrant all in one)
Study Design
Ten individual infected trees for each of the seven treatments (10 trees per treatment; 70 total trees) received herbicide applications on March 5, 2023. These trees were marked with either blue (aminopyralid) or orange (triclopyr) florescent paint (different markings for each treatment) and numbered with tree tags to aid in area delineation by treatment. Individual vine counts were performed on each tree. The tree number, vine count, and species were recorded. Treatments were evaluated at both 91-days and 122-days post-treatment. The 91-day treatments involved cutting into, but not severing, the stem tissue to determine desiccation (dryness or presence of green tissue). The second evaluation date simply looked at foliage health (either still green or brown/dead). In addition, the crown health of treated overstory “host” trees was visually assessed to determine if herbicide had impacted the merchantable trees.
Findings
The initial observation (91-days post-treatment) found minimal (ineffective) control by any of the treatments. Secondary observations (122-days) did find one of the treatments had provided good control, however. Treatment #5 (20% trycera® + 10% Cide-Kick2® + 70% diesel solution) was estimated to deaden <85% of the individual vines. The largest vines appeared to have some degree of live foliage present. Thus, retreatment using cut stem treatment (hack and squirt) is advised for these live residual vines (See Traditional Herbicide Recommendations for English Ivy below).
Other triclopyr treatments also deadened some ivy vines though both were inadequate for management purposes (treatment #4 – approximately 24% of total vines controlled; treatment #6 – approximately 10% controlled). Comparatively however, treatment #3 which only utilized 21% Trycera® in MSO without surfactant did not appear to deaden any treated English ivy vines. Likewise, all aminopyralid treatments were ineffective and did not appear to control any vines.
Overstory trees appears to be unaffected (no visual appearance of crown dieback) amongst treatments. Species composition of all sample trees included loblolly pine and hardwood species (primarily red oak, white oak, and red maple; limited yellow-poplar and gum). One smaller diameter (~7” diameter at breast height) white oak had crown damage, but this could potentially be a result of the ivy vines. Thus, findings suggest that either triclopyr acid or aminopyralid applied to vines around the base of overstory trees will not cause damage/mortality.
There are two recommendations can be derived from this study:
• Trycera® herbicide can control English ivy when mixed in the proper carrier (if adequately absorbed through the plant’s bark).
• the addition of a penetrant surfactant is necessary to ensure suppression of well-established English ivy vines. The surfactant may allow for lower concentration of active ingredient (± 20% triclopyr) to be effective.
Other important observations are:
1) aminopyralid is ineffective on English ivy regardless of the carrier/penetrant included in the solution.
2) the effective treatments took greater than three months before effects were evident.
Financial Considerations
The estimated cost per gallon of triclopyr/diesel/penetrant solution is approximately $25.56 (based on current chemical costs and diesel at $3.50 per gallon). Assuming each infected tree averages 15 vines per tree, the cost per acre (100 trees) using the same methodology applied in this study, the price per acre equates to $178.92. Labor costs are not included in this estimation. The approximate time to treat 10 trees in the study was 15 minutes and used approximately 70% of one gallon of solution.
Literature Cited
4-County Cooperative Weed Management Area. https://4countycwma.org/aweeds/best-management-practices/invasive-ivy/
Derr, J. 1993. English ivy (Hedera helix) response to postemergence herbicides. Journal of Environmental Horticulture. 11(2):45-48.
Holland, S. 2023. Herbicide usage on English ivy in the Maryville College Woods. Senior report study. Maryville College, TN. 41 P.
Miller, J. 2007. Nonnative invasive plants of southern forestry. Pages 36-37.
Miller, J., Manning, S., and Enloe, S. 2015. A management guide for invasive plants in southern forests. USDA Forest Service Southern Research Station. Asheville, NC. General Technical Report SRS-131. 133 P.
Neal, J. 1998. Postemergence, non-selective herbicides for landscape and nurseries. NC State Univ. Horticulture information leaflets. http://www.ces.ncsu/depts/hort/hil/hil-648.html.
Yang, Q., Wehtje, G., Gilliam, C., McElroy, S., and Sibley, J. 2017. English ivy (Hedera helix) control with post-emergence-applied herbicides. Invasive Plant Science and Management. 6(3): 411-415.
Author(s)
Stephen Peairs, Cooperative Extension, Forestry and Wildlife Specialist
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