In the Fall of 2013, Clemson undergraduate students set up 16 Carolina Vegetation Survey (CVS) plots in the Lower Hunnicutt restored and unrestored sections of the stream area and Hunnicutt wetland to monitor vegetative succession and plant survival of those plants introduced into each area. CVS plots allowed the students to monitor the stem count and percent cover in each plot. Realizing attempts to have minimal invasive plants in the restored section would be futile while the upstream portion of Hunnicutt Creek was heavily invaded, they expanded their survey areas. They established 25 more CVS plots in the forested parts on North Hunnicutt Creek. Initial data showed 100% native trees in the overstory but the herb, shrub, and vine strata being dominated by invasive plants. The main species of concern were and still are Chinese Privet ( Ligustrum senense), Thorny Olive ( Elagenus pungens), English Ivy ( Hedera helix), and Kudzu ( Pueraria montana).
For the purpose of undergraduate research, of the 25 CVS plots located upstream of the restoration area, four methods of removal were conducted to determine which option would provide the best results for removing the prominent understory invasive species. The methods of removal were mechanical, chemical, mechanical and chemical together, and prescribed grazing.
The main target species:
Chinese Privet ( Ligustrum sinense)
English Ivy ( Hedera helix)
Japanese Honeysuckle ( Lonicera japonica)
Kudzu ( Pueraria montana)
Mimosa ( Albizia julibrissin)
Multiflora Rose ( Rosa multiflora)
Oregon Grape ( Mahonia bealei)
Silverthorn ( Elaeagnus pungens)
Wisteria ( Wisteria sp.)
Mechanical removal involves the use of loppers, hand saws, and other hand tools to cut down plants. It also included hand pulling and the use of a root wrench. This is an environmentally friendly method of removal; however, it may not be the most efficient in comparison to other methods. Caution needs to be taken when manually removing plants so that soil is not highly disturbed, which can lead to erosion. Exposed soil may also allow easy seed germination of non-desirables. Many invasive plants can spread via rhizomes, so taking out the entirety of the root is imperative.
CLICK HERE to see a time lapse video of Clemson undergraduate researchers removing invasive species!
Two common systemic herbicides (active ingredients either glyphosate or triclopyr) are used when doing chemical control. Glyphosate absorbs into the plant tissue and is carried to the roots. This is a non-selective herbicide; caution must be taken to minimize off-target impacts. Triclopyr is a selective herbicide for broadleaf plants (forbs, shrubs, and trees). Basal bark application and foliar treatment are the main treatment methods for chemical control. Timing and seasonality are integral when planning to use a systemic herbicide because of their ability to translocate in the plant. Aquatic-friendly herbicides should also be used when in close proximity to the stream. Proper personal protective equipment should be worn when applying herbicides including long-sleeve shirts, long pants, goggles, gloves, and closed-toe shoes. The research conducted on the Clemson campus utilized both types of herbicides with foliar and basal bark treatment.
Mechanical plus Chemical:
This method of removal incorporated both the mechanical and chemical methods detailed above. This method was conducted in teams of three, one person cuts the target species, one applies herbicide to the cut stump, and another drags the cut plant to a designated pile. This was initially determined as the most effective method with minimal pesticide usage. The herbicide of choice was triclopyr which is known to be a selective herbicide for broadleaf plants (forbs, shrubs, and trees).
This method was developed and applied to an upper portion of the North Hunnicutt Creek research area so as to not interfere with other undergraduate CVS study plots. Goats were brought into the fenced study area to graze the understory for a predetermined number of days and then removed. Clemson undergraduate researchers then followed with the mechanical and chemical removal techniques described above.
Removal and Treatment Continues
Since the completion of the undergraduate study in 2016, numerous invasive species removal projects have brought the goats back to campus and employed undergraduate students to treat and remove the invasive species.