Invasive Species Management Plan_Final_Apx Figures Only_0004.pdf

Watergate Wetlands Restoration Project

Invasive Plant Species Treatment Plan

FINAL

620/167492

Delaware Water Gap National Recreation Area — 294871 June 2020

As the nation’s principal conservation agency, the Department of the Interior has the responsibility for most of our nationally owned public lands and natural resources. This includes fostering sound use of our land and water resources;

protecting our fish, wildlife, and biological diversity; preserving the environment and cultural values of our national parks and historical places; and providing for the enjoyment of life through outdoor recreation. The department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care. The department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

NPS D – 620/167492 / PMIS 294871 / June 2020

Delaware Water Gap National Recreation Area Invasive Plant Species Treatment Plan FINAL i

TABLE OF CONTENTS

INTRODUCTION

METHODS

FINDINGS

OBSERVED INVASIVE PLANT SPECIES

INVASIVE PLANT COVER

INVASIVE PLANT TREATMENT METHODS

Manual and Mechanical Control Herbicide Treatment Biological Control

TARGET INVASIVE PLANT SPECIES AND POTENTIAL TREATMENT METHODS

Herbaceous Plants Woody Vines and Shrubs Trees

INVASIVE PLANT TREATMENT IMPLEMENTATION PLAN

TREATMENT OBJECTIVES

INVASIVE PLANT TREATMENT AREAS

Provisions to Protect Native Plants Provisions to Protect Rare Plants

INVASIVE PLANT CONTROL MEASURES

Material Disposal Herbicide Use

AQUATIC PESTICIDE PERMIT

CONTRACTOR LICENSING

DELIVERABLES

TREATMENT SCHEDULE

MONITORING AND MAINTENANCE

ACRONYMS AND ABBREVIATIONS

REFERENCES

ii

LIST OF TABLES

Table 1. Invasive Non-native Plant Species Observed in the Project Area, including their Wetland Indicator Status

Table 2. Estimated Range in Percent Cover by Invasive Plant Species and Acreage of Each Map Unit

Table 3. Total Acreage and Percentage of Project Area of Each Percent Cover Class

Table 4. Invasive Non-native Plant Species Targeted for Treatment in the Project Area

Table 5. Potential Control Methods for Targeted Invasive Plant Species in the Project Area

Table 6. Recommended Herbicides and treatment methods to Control target Invasive Plants

Table 7: Construction phase Species-specific Treatment Schedule for Target Invasive Plants in the Project Area

Table 8: Monitoring and Maintenance phase (Years 1 to 3) Species-specific Treatment Schedule for Target Invasive Plants in the Project Area

APPENDIXES

Appendix A—Report Figures

Appendix B—Species Fact Sheets for Priority Invasive Plants in the Project Area

Appendix C—Labels of Recommended Herbicides

Appendix D—Safety Data Sheets of Recommended Herbicides iii

EXECUTIVE SUMMARY

The National Park Service (NPS) proposes to restore wetlands and the natural function of Van Campens Brook at the Watergate Recreation Site by removing artificial dams and human-made ponds and reestablishing the connection between Van Campens Brook and its floodplain. The project would result in a more natural and high-functioning wetland and riparian floodplain system, improved floodplain connectivity within the project area, and more natural fluvial dynamics in Van Campens Brook. In support of this effort, reference site (wetlands) and reference reach (stream) evaluations were conducted to understand the composition and function of regional habitats similar to those desired at the Watergate site.

This report evaluates the extent of invasive non-native plant species in the project area and provides recommendations for the treatment and removal of the predominant invasive plant species. It includes a list of invasive plant species present in the project area and defines the species prioritized for treatment to promote the restoration of desirable native plant communities

A review of previous reports and a field survey of the project area was completed to identify invasive plant species present. As part of the field survey, observations of the total percent cover provided by invasive plants and the primary species accounting for the cover were recorded, and the extent of each area was approximated on aerial maps. Twenty-four invasive plant species were identified in the project area, and of those, 14 plants have been identified as the prioritized targets for treatment based on the species extent and influence on the habitats in which they occur and availability of effective treatments.

The project area was divided into 44 discrete map units with different percent cover classes based on total cover provided by invasive plant species. Most of the project area (68%) falls within the percent cover classes exceeding 60% cover by invasive plants. In general, invasive shrub species in the forest understory consisting of Japanese barberry, autumn olive, bush honeysuckles, and multiflora rose were observed to be the primary source of the high cover estimates.

The report includes a recommended treatment plan, treatment schedule, and guidance on treatment implementation. The objective of the treatment plan is to reduce the extent of targeted invasive plant species in the project area in the most efficient manner to promote the restoration of desirable native plants. A goal of the plan is to produce measurable results over the three- to five-year management period of the project consistent with NPS Management Policy 4.4.4.2, Removal of Exotic Species Already Present (NPS 2006).

iv

This page intentionally left blank.

INTRODUCTION

The National Park Service (NPS) proposes to restore wetlands and the natural function of a stream and its floodplain by reversing human-made changes in and near the Watergate Recreation Site in Hardwick Township, Warren County, New Jersey. The project would compensate for temporary and permanent impacts on wetlands, floodplains, and ecosystem function caused by the construction, operation, and maintenance of a high-voltage transmission line and its 200-foot right-of-way within the Delaware Water Gap National Recreation Area (DEWA).

WSP USA, Inc. (WSP) was hired to perform predesign, schematic design, and design development, and provide construction documents and supplemental services for the NPS DEWA Watergate Wetlands Restoration Project (project) (figure 1 in appendix A). The principal project goal is to generate 33-credit acres of wetland mitigation through reestablishment of palustrine wetland habitat and hydraulic restoration of Van Campens Brook. The project would result in a more natural and high-functioning wetland and riparian floodplain system, improved floodplain connectivity in the project area, and more natural fluvial dynamics in Van Campens Brook.

The approximately 114-acre project area is located in Hardwick Township in Warren County, New Jersey. The project area includes a segment of Van Campens Brook and its associated floodplain, a New Jersey Department of Environmental Protection (DEP) Category 1 waterway and designated trout production stream, whose contributing watershed is solely contained within NPS property.

Historical modifications, including land clearing, grading, and damming of the brook to create a series of ponds, historical farming fields, and homestead sites (now recreational trails and picnic areas), substantially degraded on-site habitat, which was further impaired by non-native invasive vegetation throughout the project area.

This report summarizes the findings for Task Order 2, subtask 1.5.4, Invasive Plant Species Treatment Plan. The plan presents the results of botanical survey of the project site to identify the invasive non-native plant species and their relative cover in the project area. The report includes a list of invasive plants present in the project area, defines the invasive plants prioritized for treatment and removal, and establishes management goals for the project that are achievable, cost-effective, and will produce measurable results over the management period of the project consistent with NPS Management Policy 4.4.4.2, Removal of Exotic Species Already Present (NPS 2006).

METHODS

The WSP team conducted a wandering survey of the entire project area in late September/early October 2019 to identify the presence and extent of invasive plants. An initial list of the observed non-native plant species was generated for the site using the results of the survey and information collected from the fall rare plant survey. The list may be updated based on findings from the spring rare plant survey.

The definition of plant species as invasive and non-native in based on the following definitions:

Non-native species: Species that occupy or could occupy park lands directly or indirectly as the result of deliberate or accidental human activities (NPS 2006).

Invasive species: With regard to a particular ecosystem, a non-native organism whose introduction causes or is likely to cause economic or environmental harm, or harm to human, animal, or plant health (Executive Order 13751).

During the field inspection, WSP divided the site into multiple map units with similar physical or plant community characteristics. Within each map unit, an ocular estimate of the total percent cover of invasive plants was estimated and assigned to a range of total cover. The percent cover range is an estimate of the average condition for each map unit. A list of the predominant invasive plants in each map unit was also recorded. The boundary of each map unit was drawn on an aerial map and represents an approximation of the limits of each area. From this information, a treatment plan was developed that focuses on cost effective and attainable results and protects sensitive habitats.

FINDINGS

OBSERVED INVASIVE PLANT SPECIES

Invasive plants are non-native species that rapidly and aggressively spread into natural or human-altered plant communities and are capable of displacing native species, altering the community structure, and potentially disrupting the function of ecosystem processes. New Jersey does not have an official list of invasive plant species, but the New Jersey Invasive Species Council (2009a, b) has identified numerous priority invasive plant species (see Snyder and Kaufman 2004).

According to NPS (2017), upland ecosystems at DEWA are threatened by tree-of-heaven (Ailanthus altissima), autumn olive (Elaeagnus umbellata), multiflora rose (Rosa multiflora), oriental bittersweet (Celastrus orbiculatus), Norway maple (Acer platanoides), and honeysuckle species (Lonicera spp.).

Wetland and riparian areas are threatened by multiflora rose, Japanese barberry (Berberis thunbergii), honeysuckle species, autumn olive, purple loosestrife (Lythrum salicaria), common reed (Phragmites australis), knotweed (Polygonum spp.), garlic mustard (Alliaria petiolata), Nepalese browntop (Microstegium vimineum), and multiflora rose (Perles, Callahan, and Marshall 2010).

A review of the previously completed wetland delineation report (JMT 2017a) and forest inventory report (JMT 2017b) revealed that several invasive plants were observed during these investigations in a subset of the current project area. These species included Nepalese browntop (also known as Japanese stiltgrass), Japanese barberry, multiflora rose, autumn olive, European privet (Ligustrum vulgare), bush honeysuckle wine raspberry (Rubus phoenicolasius), purple loosestrife, small carpetgrass (Arthraxon hispidus), and reed canarygrass (Phalaris arundinacea). One aquatic plant, parrot feather watermilfoil (Myriophyllum aquaticum) was reported present in several ponds. The reports also identified other non-native plants such as Norway spruce (Picea abies) and common plantain (Plantago major) that are not considered invasive species in this region.

Table 1 provides a compiled list of invasive plants observed in the project area based on the studies listed above and the 2019 fieldwork completed for this report. The additional botanical surveys planned for spring 2020 may identify a few additional species; however, the primary invasive plants are included in this list. Most of the species in table 1 are also considered priority invasive plant species in New Jersey.

TABLE 1. INVASIVE NON-NATIVE PLANT SPECIES OBSERVED IN THE PROJECT AREA,

INCLUDING THEIR WETLAND INDICATOR STATUS

Scientific Name Common Name Growth Form Wetland Indicator

Status

Acer platanoides Norway maple Tree UPL

Ailanthus altissima Tree-of-heaven Tree FACU

Alliaria petiolata Garlic mustard Biannual forb FACU

Artemisia vulgaris Common wormwood (mugwort) Perennial forb FACU

Arthraxon hispidus Small carpetgrass Annual grass FAC

Berberis thunbergii Japanese barberry Shrub FACU

Celastrus orbiculatus Oriental bittersweet Woody Vine FACU

Elaeagnus angustifolia Russian olive Shrub FACU

Elaeagnus umbellata Autumn olive Shrub UPL

Euonymus alatus Burning bush Shrub FACU

Glechoma hederacea Ground ivy Perennial forb FACU

Ligustrum vulgare European privet Shrub FACU

Lonicera japonica Japanese honeysuckle Herbaceous vine

FACU

Lonicera morrowii Morrow's honeysuckle Shrub FACU

Lonicera tatarica Tartarian honeysuckle Shrub FACU

Lythrum salicaria Purple loosestrife Perennial forb FACW

Mentha x piperita Peppermint Perennial forb FACW

Microstegium vimineum Nepalese browntop Annual grass FAC

Myriophyllum aquaticum Parrot feather watermilfoil Aquatic Forb OBL

Phalaris arundinacea Reed canary grass Perennial grass FACW

Polygonum cuspidatum Japanese knotweed Perennial forb FACU

Rosa multiflora Multiflora rose Shrub FACU

Rubus phoenicolasius Wine raspberry Subshrub FACU

Vinca minor Common periwinkle Woody Vine UPL

SOURCE: USDA-NRCS 2019

KEY TO INDICATOR CATEGORIES:

OBL: OBLIGATE WETLAND, ALMOST ALWAYS OCCUR IN WETLANDS.

FACW: FACULTATIVE WETLAND, USUALLY OCCUR IN WETLANDS, BUT MAY OCCUR IN NON-WETLANDS.

FAC: FACULTATIVE, OCCUR IN WETLANDS AND NON-WETLANDS.

FACU: FACULTATIVE UPLAND, USUALLY OCCUR IN NON-WETLANDS, BUT MAY OCCUR IN WETLANDS.

UPL: OBLIGATE UPLAND, ALMOST NEVER OCCUR IN WETLANDS.

N/A: NOT AVAILABLE (GENUS IDENTIFICATION ONLY).

INVASIVE PLANT COVER

As noted above, the plant communities in the project area were visually assessed for the range in percent cover composed of invasive plants. The project area was divided into different map units based on the estimated percent cover of invasive plants. Figure 2 (appendix A) depicts the location and extent of each map unit classified by the estimated invasive plant cover range. Table 2 provides a summary of each invasive species map unit and the estimated range in percent cover observed within these areas. In general, invasive shrub species in the forest understory and scrub shrub habitats consisting of Japanese barberry, autumn olive, bush honeysuckles, and multiflora rose were observed to be the primary source of the high cover estimates. The picnic grounds with mowed lawn dominated by cool season grasses (Map Unit 9) were the only location with nearly 100% non-native cover. The map units were observed to have some variability in cover provided by invasive plant cover, changes in species dominance, and some blending with adjoining map units. In general, invasive woody shrubs were present in all map units, whereas some herbaceous species and vines (e.g., Nepalese browntop, oriental bittersweet, ground ivy, periwinkle, common wormwood, and Japanese knotweed) were less consistently observed or were primarily observed in discrete patches.

TABLE 2. ESTIMATED RANGE IN PERCENT COVER BY INVASIVE

PLANT SPECIES AND ACREAGE OF EACH MAP UNIT

Invasive Species Map Unit

Estimated Range in Percent Cover

Acreage

1 80-90% 1.95

2 70-80% 4.70

3a 60-70% 1.10

3b 10-20% 1.01

4 50-60% 1.36

5 20-30% 0.60

6a 60-70% 3.91

6b <5% 0.30

7a 30-40% 3.31

7b 70-80% 1.01

8 80-90% 0.76

9 90-100% 4.72

10a 80-90% 0.42

10b <5% 0.32

11 80-90% 1.99

12 10-20% 0.53

13a 80-90% 6.47

13b 40-50% 0.25

13c 10-20% 0.29

13d 5-10% 0.77

14 80-90% 2.64

Invasive Species Map Unit

Estimated Range in Percent Cover

Acreage

15a <5% 1.16

15b 80-90% 2.04

15c 70-80% 3.06

15d <5% 5.46

15e 10-20% 1.76

15f 70-80% 3.36

15g 20-30% 0.99

15h 30-40% 0.35

16 50-60% 2.12

17a 70-80% 6.41

17b 80-90% 2.32

17c <5% 0.60

17d <5% 0.74

18a 70-80% 2.89

18b 60-70% 0.98

18c <5% 0.22

18d <5% 0.24

19a 5-10% 1.10

19b <5% 0.69

19c 80-90% 1.17

19d 60-70% 0.11

20 80-90% 1.41

21 <5% 1.09

Total 78.67

The summary in table 3 provides the acreage and percentage of the project area by each percent cover class. Most of the project area (68%) falls within the percent cover classes exceeding 60% cover by invasive plant species. The two cover classes with less than 10% cover by invasive plants represent the least affected plant communities and account for approximately 16% of the project area. Sensitive habitats in the project area are generally associated with locations with less than 5% invasive plant cover and include wetlands and a mixed oak forest community (e.g., Map Unit 10b).

TABLE 3. TOTAL ACREAGE AND PERCENTAGE OF PROJECT AREA OF EACH PERCENT COVER CLASS

Percent Cover Class Total Acreage Percentage of Project

Area

<5% 10.83 13.8%

5–10% 1.88 2.4%

10–20% 3.58 4.6%

20–30% 1.59 2.0%

30–40% 3.66 4.7%

40–50% 0.25 0.3%

50–60% 3.48 4.4%

60–70% 6.10 8%

70–80% 21.42 27.2%

80–90% 21.17 26.9%

90–100% 4.72 6%

Total 78.67 100%

INVASIVE PLANT TREATMENT METHODS

Methods of invasive plant management can include mechanical, chemical, and/or biological treatments. Successful invasive plant control often requires the combination or sequential use of various control methods. The method selected depends on the extent and type of infestation; the amount of native vegetation on-site; and the time, labor, and other resources available. This section contains a general discussion of mechanical and chemical control methods for each invasive plant species found in the project area. Species-specific considerations and recommendations are provided in the next section. Further information about various control methods for the targeted invasive plants species is provided in the fact sheets in appendix B.

Eliminating invasive plants requires diligence because of the abundant seed production and strong vegetative reproduction properties that make these species so invasive. Regardless of the treatment method selected, treated plants should be rechecked one or more times a year, and any new sprouts, suckers, or seedlings treated (cut, sprayed, or pulled) as soon as possible, especially before they rebuild root reserves. Because most invasive plants found in the project area colonize disturbed areas, establishing a thick cover of native plants helps shade out and discourage invasive plants from establishing.

Manual and Mechanical Control

Manual and mechanical control of invasive plants is viable for some species in the project area. These methods involve removing invasive plants by hand or with tools or heavy equipment via pulling, cutting, mowing, girdling, mulching, or otherwise damaging the plants. An advantage to manual and mechanical control is that it minimizes damage to desirable plants and animals; however, it is generally more labor intensive. Thus, manual and mechanical control techniques are generally only recommended for small infestations and/or where a large pool of volunteer labor is available. Also, multiple treatments are often necessary to prevent the invasive plant from reestablishing, and the disturbance may create conditions for reinvasion by the same or other invasive plants. Manual and mechanical control techniques are not effective for all herbaceous invasive plants and may even cause some to vigorously resprout from fragments of roots or other plant material left in the soil.

These control methods are therefore often used in combination with other techniques (e.g., after plants are pulled or cut, resprouts and seedlings are later treated with herbicides) (Tu, Hurd, and Randall 2001).

When pulling plants, the root mass must be removed to the greatest extent possible to prevent resprouting later. It is also important to remove all plant parts by removing them off-site and disposing of them in black plastic garbage bags or burning them. Woody plants (trees, shrubs, and vines) can be cut at ground level with clippers or manual or power saws. Cutting is most effective before plants have begun to flower to prevent seed production, especially for herbaceous species;

however, most plants respond to cutting by producing new sprouts, so follow-up treatments are often necessary. Effective tools for uprooting small woody plants are those that apply leveraged pressure to remove root systems on woody plants with trunk diameters up to 2.5 inches.

Herbicide Treatment

Chemical herbicides are an important tool in invasive plant control efforts. Herbicides available for invasive plant management fall into several categories. They can be selective or non-selective.

Selective herbicides kill only certain plants but not others, while non-selective herbicides kill almost any plant species. Also, some herbicides kill the plant on contact, while systemic herbicides are absorbed into the plant. Systemic herbicides may kill plants by disrupting cell membranes, inhibiting the production of amino acids or the synthesis of lipids, or otherwise negatively affecting a plant’s metabolism. Most selective herbicides are also systemic herbicides. Lastly, herbicides can be classified as pre-emergent or post-emergent. Pre-emergent herbicides are applied to soil before seeds germinate to prevent seeds from sprouting and inhibiting the formation of plant tissue.

Post-emergent herbicides control existing plants but do nothing to stop new plants from germinating from seeds.

Two of the most commonly used herbicides available under multiple brand names are glyphosate and triclopyr. The label on the herbicide package is valuable for understanding the proper use of an herbicide. Appendix C provides the labels of the common brand names recommended in this plan, which list the types of weeds controlled, the correct time to apply the product, and the proper amount to use. The labels also state where the product can be used, if any protective clothing is necessary during application, and any dangers to other biota.

Glyphosate is a non-selective systemic herbicide that is relatively slow acting and has low toxicity.

Glyphosate (e.g., Roundup®, Rodeo®, Accord®) will kill or injure almost any plant, herbaceous or woody, contacted by the spray, and it may kill non-target plants that are only partially sprayed. It is labeled for aquatic use and for foliar and cut stump applications, and some forms are specifically formulated for aquatic sites (e.g., AquaMaster®). An aquatically registered surfactant (see the labels in appendix C) will need to be added to the glyphosate solution for good results.

Triclopyr (e.g., Garlon® 3A, Garlon® 4) is a selective systemic herbicide that affects only broadleaf herbaceous and woody plants without injuring grasses, sedges, or rushes. It should be considered in areas where native or other desirable grasses are meant to be conserved. Triclopyr is one of the most popular and safest herbicides used in natural areas (The Nature Conservancy 2010). Opinions differ about whether glyphosate or triclopyr is more effective at woody plant control, but both are similarly effective relative to many stronger restricted-use herbicide active ingredients, such as picloram or imazapyr (Tu, Hurd, and Randall 2001). Triclopyr is often used for brush control in rights-of-way and natural areas. It comes in several different formulations and can be used for foliar, cut stump, and basal bark applications; some formulations are labeled for aquatic use. Each triclopyr formulation has very different specific uses, hazards, and precautions. Both glyphosate and triclopyr have low soil activity, so they do not pose a threat to groundwater if applied properly and at recommended label rates.

Surfactants should be applied in combination with most herbicides to facilitate plant uptake through the meristematic tissue. Surfactants help the herbicide stick to plant foliage or penetrate the outer layer by reducing the surface tension of water. Surfactants are already included in some formulations such as Roundup® and many other glyphosate products. Some uses do not require surfactants, such as triclopyr or glyphosate, when applied cut stump. A colorant or dye can also be added to the herbicide to help distinguish treated from untreated plants.

Three common types of herbicide application are: (1) cut stump method, (2) basal bark application, and (3) foliar application. For large shrubs and trees that cannot be easily sprayed without damaging adjacent vegetation, the cut stump method is recommended. This method involves cutting and removing the growing plant stems and applying herbicide to the exposed cambium (i.e., inner bark) of the remaining rooted stem/stump with a paintbrush or backpack sprayer. Glyphosate should be applied within 5 to 15 minutes after cutting, but triclopyr ester formulations have no such time limit, except with root suckering species. The herbicide is then be translocated into the plant’s root system, especially when cut stump treatments are implemented in the fall. The method can also be effective during winter and early spring before sap starts flowing up the stem to the branches. The main advantage of the cut stump method is that it allows for a high level of control over the location and amount herbicide application, and thus it has a low probability of affecting non-target plants or causing other environmental contamination. It also requires a relatively small amount of herbicide to be effective. However, because the herbicide is concentrated, a large amount of chemical can be necessary for large infestations. This method is also effective for invasive vines that climb native, desirable trees (Tu, Hurd, and Randall 2001).

Basal bark application is another method for controlling invasive woody plants where glyphosate or triclopyr is sprayed or painted on the bark at the base of a tree or shrub. A mixture of 25% triclopyr and 75% oil (e.g., mineral oil or vegetable oil) is applied to the base of the tree trunk to a height of 12 to 15 inches from the ground. The herbicide is usually mixed with an oil to allow it time to penetrate the bark. Basal bark treatment works best on young trees less than 6 inches diameter with smooth bark. It is not usually effective against older plants with thick bark (Tu, Hurd, and Randall 2001).

This method works during spring through fall, but it should be avoided in late winter/spring during heavy sap flow periods and in the first three months after leaf fall in autumn. The basal bark of the tree stem must be free of snow, ice, or water, although precipitation following application is not a problem (NPS and USFWS 2010). The stem should be completely wetted and sprayed until run-off is noticeable at the ground. A dye mixture is also helpful to track sprayed plants.

Lastly, foliar applications involve spraying herbicide on the leaves of target species. This treatment is most effective when applied with a surfactant in the early fall while leaves remain on the plant and sugars are being translocated to the plant’s root system. Plants are beginning to increase their translocation of carbohydrates and amino acids in their roots during this period and will accumulate herbicides. Foliar herbicides can also be applied to young, actively growing plants prior to flowering.

If the plants are too mature for effective herbicide application, a common practice is to mow an invasive plant infestation prior to seed maturation, allow the plants to regrow to a height of 2 to 4 feet (depending on species), and then apply herbicide to the new growth. This process weakens the plant, prevents spread by seed, and maximizes the effectiveness of the herbicide application. Foliar application may need to be repeated two or three times over consecutive years. Compared to the cut stump and basal bark methods, foliar applications require more herbicide (Tu, Hurd, and Randall 2001).

Biological Control

Biological control of invasive plants involves using living organisms such as parasites, pathogens, or predators to control their growth and reproduction. For some invasive plant species, biological control is the only tool proven effective at controlling widespread infestations. However, biological control agents are usually imported from the natural range of an invasive plant; they are often exotic species themselves and care must be taken to ensure they do not become pests to other native species. Among the targeted species in the project area, none of the species currently have an approved biological agent available. Purple loosestrife is not included on the targeted list of species based on the field observation of its low percent cover within emergent wetlands in the project areas;

however, biological control for this species is readily available should it be required.

TARGET INVASIVE PLANT SPECIES AND POTENTIAL TREATMENT METHODS

Cost effective management of invasive plants in the project area require control options that are effective, cost-efficient, and feasible to implement. WSP evaluated the current knowledge around various management options for each invasive plant species observed in the project area. Factors considered include the extent of the species’ distribution and abundance, the probability of reinvasion, the potential management costs, and the potential impacts of control on non-target plants. Based on this information, table 4 provides a list of 14 invasive plant species targeted for treatment in the project area.

A brief description of each of the targeted species for treatment is provided below. Further information about each target invasive plant can be found in appendix B, which contains multiple fact sheets for each species, provided by DEP, the US Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS), the Plant Conservation Alliance, and other natural resources agencies. In addition, a discussion of the potential control strategies for the targeted invasive plant species is provided after each species description, followed by the recommended steps for the execution of the treatment. This information will be used to develop the project specifications that will direct the execution of the work by a contractor.

Herbaceous Plants

Most herbaceous plants can be pulled by hand, and this treatment strategy is recommended for early detections of invasive herbaceous plants in the project area. While repeated mechanical control methods (e.g., mowing) can be effective, these methods are not feasible for most targeted populations in the project area because of the potential harm to native species. The decision to apply herbicides is not taken lightly, especially on NPS lands. However, in instances where manual control is not practical, the use of herbicides is recommended. Some of the drivers for herbicide use include the reduced efficacy of hand pulling species with extensive or deep root systems that can resprout and in areas with extensive cover because of the large extent of the invasive plant population(s).

Glyphosate is the recommended non-selective systemic herbicide because it is absorbed by plants and carried to the roots, and it kills the entire plant. Foliar application can be made by spraying herbicide such that the herbicide mix thoroughly covers most leaves but does not drip off the leaves.

To provide for ample drying time, applications should be made when rain is unlikely for about 12 hours after application and leaves should be dry prior to treatment. Also, air temperature should be above 65 degrees Fahrenheit (°F) to ensure absorption by the plants. Spraying should be conducted when wind speeds are less than 10 miles per hour to avoid off-site drift, and it is important to prevent spray contact with desirable plants. Foliar treatments should be done either in early spring when most other non-target vegetation is dormant or mid to late summer and fall when plant growth slows, and resources are being sent to the roots. The manufacturer’s label provides specific information and restrictions regarding the use of herbicides (see appendix C).

TABLE 4. INVASIVE NON-NATIVE PLANT SPECIES TARGETED FOR TREATMENT

IN THE PROJECT AREA

Scientific Name Common Name

Acer platanoides Norway maple

Ailanthus altissima tree-of-heaven

Artemisia vulgaris Common mugwort

Berberis thunbergii Japanese barberry

Celastrus orbiculatus Oriental bittersweet

Elaeagnus angustifolia Russian olive

Elaeagnus umbellata autumn olive

Euonymus alatus burning bush

Glechoma hederacea ground ivy

Ligustrum vulgare European privet

Lonicera morrowii Morrow’s honeysuckle

Lonicera tatarica Tartarian honeysuckle

Polygonum cuspidatum Japanese knotweed

Rosa multiflora multiflora rose

Vinca minor common periwinkle

Application rates should follow the manufacture’s herbicide labels for the target species being treated. These herbicide labels list information on proper use, rate, and timing of application;

storage; cleanup; and emergency procedures. Safety data sheets for some of the commonly used herbicides are also provided in appendix D. All herbicide use should be in accordance with label instructions and state and federal laws (including adjacent landowner notification requirements) and be conducted by or under the supervision of certified applicators.

All sites where herbicides are applied should be inspected three to four weeks post application to assess the effect of the treatment on target and non-target plants and to determine if natural revegetation by native or non-invasive plants is occurring or if additional restoration through seeding and planting may be required.

A summary of recommended control methods of target species of herbaceous plants is provided in table 5. Further species-specific recommendations are provided below.

TABLE 5. POTENTIAL CONTROL METHODS FOR TARGETED INVASIVE PLANT SPECIES IN THE PROJECT AREA

Species Name

Common Name

Associated Habitats Recommended Control Methods

Effective Herbicides Notes

Artemesia vulgaris

Common wormwood

Open fields, wood margins, disturbed areas

Hand pulling; Foliar herbicide application several times during the growing season

Aminopyralid, Clopyralid, Glyphosate, Imazapyr

Individual plants can be easily hand pulled but root fragments will resprout.

Rhizomes must be thoroughly dried and removed from site or burned to avoid regeneration.

Eradication may take several years.

Glechoma hederacea

Ground ivy Shady ground, woodlands, usually around structures

Hand pulling; Foliar application Glyphosate, Triclopyr, Imazapyr

Cut stems and rhizomes must be thoroughly dried and removed from the site or burned to avoid regeneration.

Polygonum cuspidatum

Japanese knotweed

Utility right-of-way, along waterways, low-lying areas, disturbed areas

Mechanical control is not recommended.

Stem injection likely most effective (see Soll 2004).

Foliar application and cut stump treatment are also effective.

Glyphosate, Imazapyr

Cut stems and rhizomes must be thoroughly dried and removed from the site or burned to avoid regeneration.

Eradication may take several years due to extensive rhizome system.

Vinca minor Common periwinkle

Shady sites, including forests

Hand pulling; Foliar application Triclopyr Physical removal of rhizome is difficult.

Oil-based herbicides like triclopyr mixed with mineral oil are more effective.

Berberis thunbergii

Japanese barberry

Disturbed areas, forest edges, open woodlands, and riparian areas

For small populations, manual control is effective as long as the root system is removed.

For larger infestations, manual control may need to be combined with chemical treatments.

Use triclopyr or glyphosate for cut stumps or as basal bark treatment.

Glyphosate, Triclopyr

Use thick gloves for manual control to avoid injury from the spines.

Hand pulling requires complete removal of root system to prevent resprouting.

Herbicide treatment is best in winter when other plants are dormant because barberry’s green leaves allow easy identification.

Species Name

Common Name

Associated Habitats Recommended Control Methods

Effective Herbicides Notes

Celastrus orbiculatus

Oriental bittersweet

Forest edges, forest gaps, fencerows, old fields

Small plants can be easily hand pulled from moist soils.

Foliar application is suitable for large infestations without desirable native plants.

Basal bark treatment is best for stems < 1 inch in diameter.

Glyphosate, Triclopyr

To avoid seed dispersal, it is important that cut plant parts are disposed of properly off site.

Elaeagnus angustifolia Elaeagnus umbellata

Russian olive autumn olive

Disturbed areas, roadsides, pastures, fields, forest edges, and open woodlands

Seedlings can be dug out when the soil is moist to ensure removal of the root system.

High-volume foliar treatments to individual small trees (smaller than 6 feet in height).

Low-volume basal bark or cut stump herbicide applications to large trees (greater than 6 feet in height).

Triclopyr Cutting will encourage resprouting.

To control larger plants, basal or cut stump applications are recommended late in the growing season or dormant season.

Glyphosate is effective.

Foliar applications may be adequate for small patches and the best time.

Euonymus alatus

Burning bush Fields, woodland borders, open woodlands, and mature forests

Use manual control for small populations and for relatively small plants.

Perform cut stump methods using glyphosate or triclopyr ester.

For larger stems, use basal bark application of triclopyr.

Glyphosate, Triclopyr, Imazapyr

Foliage is not palatable to deer, so it tends to increase in areas with excessive deer browsing.

Ligustrum vulgare

European privet

Floodplains, fields, disturbed forest understory, and forest edges

Use manual control for small populations and for relatively small plants.

Perform cut stump methods using glyphosate or triclopyr ester.

For larger stems, use basal bark application of triclopyr.

Glyphosate, Triclopyr, Imazapyr

Control requires follow-up treatments for seedlings and sprouts.

Species Name

Common Name

Associated Habitats Recommended Control Methods

Effective Herbicides Notes

Lonicera spp. Bush honeysuckle

Forest edges, thickets, floodplains, maritime forests, disturbed areas

Pull or dig up individual shrubs in small populations where herbicides cannot be used.

Herbicide control can be done using a cut stump treatment with glyphosate, triclopyr amine, or triclopyr ester.

Basal bark spray treatment around the stem with triclopyr ester or spraying the leaves with a glyphosate solution is also effective.

Glyphosate Any portions of the root system not removed can resprout.

Winter clipping should be avoided because it encourages vigorous resprouting.

Heavy deer populations limit regrowth.

Rosa multiflora

Multiflora rose

Forest edges, riparian areas, fields, gaps in woodlands

Pull or dig up individual young shrubs.

Cut or mow at base repeatedly throughout growing season, but it may take six years for control.

Foliar herbicide is effective after two years of application.

The cut stump method may be the most effective.

Glyphosate, Triclopyr

Cutting stumps in established thickets is very difficult because of the numerous thorny branches.

Ailanthus altissima

Tree-of-heaven

Disturbed areas, roadsides, forest and field edges, and urban areas

Pull or dig up young seedlings.

For larger trees, notch trunk with an axe and squirt systemic herbicide into cut in late summer.

Basal bark treatment is most effective spring through fall but should avoid late winter/spring during heavy sap flow periods and the first 3 months after leaf fall in autumn.

Glyphosate, Triclopyr, Imazapyr

Cutting will encourage resprouting.

It is important to remove all root fragment if tree is pulled.

Exposure to sap can cause nausea, headaches, and heart problems.

Acer platanoides

Norway maple

Forest, fields, most commonly found in urban and suburban natural areas and urban woodlots

Seedlings can be pulled by hand or with a weed wrench.

Small to large trees can be cut to the ground, repeating as necessary to control any regrowth from sprouts.

Foliar application or cut stump application with systemic herbicide is effective.

Glyphosate, Triclopyr

Control requires follow-up treatments for seedlings and sprouts.

SOURCES: SPECIES FACT SHEETS (APPENDIX B), MILLER, MANNING, AND ENLOE 2015; MCHUGH 2006; NPS AND USFWS 2010; TU, HURD, AND RANDALL 2001

Common Wormwood (Mugwort) (Artemisia vulgaris)

Native to Africa, temperate Asia, and Europe, common mugwort is a perennial weed that is difficult to control because of its ability to spread by underground rhizomes. It is in the Artemesia genus of the Aster family, which contains numerous herb and ornamentals species. At a glance, leaves are similar in appearance to chrysanthemum. They are 2 to 4 inches long, 1 to 3 inches wide, simple, alternate, deeply lobed, and have a distinctive aroma. Leaf undersides are covered with soft, white to gray hairs. Common wormwood has vigorous underground rhizomes.

Common wormwood removal can be completed through combined repeated cutting, hand pulling of rhizomes, and foliar application of a systemic herbicide. Manual control of small patches can reduce but not eliminate the species because it requires removing the entire rhizome to avoid resprouting. For small patches, spot-treatments of glyphosate can be effective (Bing 1983). Large patches require herbicide treatment. Glyphosate applied in late summer or early fall will suppress wormwood the following year but generally not eradicate it. Bradley and Hagood (2017) reported very effective long-term wormwood control using relatively low use rates of picloram and clopyralid, and higher rates of glyphosate and dicamba.

Ground Ivy (Glechoma hederacea)

Ground ivy occurs throughout the US in the contiguous 48 states except for Nevada, Arizona, and New Mexico and has been reported to be invasive in natural areas from Wisconsin to Connecticut, south to Tennessee and North Carolina. It is common in moist areas such as floodplains, low woods, and disturbed sites and is a significant weed in lawns. Ground ivy grows on damp, heavy, fertile, and calcareous soils and does not tolerate highly acidic or saline soils. Ground ivy is a vigorous grower that spreads across the ground forming dense patches that push out native plants. It is toxic to many vertebrates, including horses, if eaten in large quantities either fresh or in hay.

Ground ivy is difficult to control once established because it is hard to remove all root and stolon fragments. Seed banks may also remain viable after control methods are used. Small patches can be pulled by hand or using a rake when the soil is damp, but all roots and stolen fragments must be removed. Otherwise, chemical control using a systemic herbicide can be effective. A rust fungus, Puccinia glechomatis attacks ground ivy causing severe damage or death and may hold some potential for biological control but is not available for use (see DiTommaso and Weston 2001).

Japanese Knotweed (Polygonum cuspidatum)

Japanese knotweed occurs across the continent from Maine to Wisconsin, south to Louisiana, and in scattered locations in the Midwest and Western states. It can tolerate a variety of adverse conditions, including deep shade, high temperatures, high salinity, and drought. Japanese knotweed is commonly found near water sources, such as along streams and rivers, in low-lying areas, waste places, utility rights-of-ways, and around old home sites. It spreads quickly by stem and rhizome, and occasionally seed, to form dense thickets that exclude native vegetation and greatly alter natural ecosystems. Japanese knotweed poses a significant threat to riparian areas where it can survive severe floods and rapidly colonize scoured shores and islands. Once established, populations are extremely persistent. Frost kills the plant above ground, but it can still spread from deep underground rhizomes or roots. It affects native plants via allelopathy, whereby chemicals in the roots exclude other plants nearby. Small pieces of the plant can root and grow.

Japanese knotweed is difficult to eradicate, even with herbicides. Hand cutting, mowing, or other methods are generally not effective for managing knotweed because stem fragments can root at the nodes and generate new plants (USDA-NRCS n.d.a; NPS 2015). McHugh (2006) and other guidance caution that repeated cutting tends to produce lots of small stems, which could make future treatment more difficult. Similarly, repeatedly digging or pulling to uproot plants only eliminates a portion of the root system and is only feasible for very small patches (USDA-NRCS n.d.a). Soll (2004) provides best management practices for developing a management strategy for Japanese knotweed.

Manual control can be an integral part of managing Japanese knotweed, particularly when designed to promote even foliar cover for later herbicide application in late summer or fall when plants are translocating resources to the rhizome (Jones et al. 2018). A spring spray or cutting sets back the plant so that it can be sprayed at an effective height and growth stage later in the year. If feasible, spring cutting may reduce total herbicide load into the watershed and may be more labor efficient than spraying twice. McHugh (2006) noted little difference in effectiveness of cutting the plant in the spring and spraying in the late summer/early fall versus spraying both times.

Glyphosate is the most recommended chemical for treating Japanese knotweed. Another herbicide that may be considered for knotweed control is Imazapyr (e.g., Arsenal®). To successfully control knotweed with herbicide, the active ingredient in the herbicide product must have a mode of action designed to move the chemical from the leaves into the root system at sufficient concentration to kill the root tissue. Differing levels of success have been reported for the same chemical on different sites, likely due to differences in the amount of root mass underground. The Michigan Department of Natural Resources (MDNR) concludes that Imazapyr has shown the greatest documented effectiveness on this species to date but cautions that it can cause significant damage to other plants in the area and may not be appropriate in areas with desirable native species. DEWA has also demonstrated the effectiveness of knotweed control using imazapyr. Sites where imazapyr has been used should not be planted for at least one year because of its lingering effects (MDNR 2012a). In addition to foliar application and cut stump treatments, the herbaceous stems of Japanese knotweed can be injected with herbicide using a needle and syringe, which is more labor intensive and uses more herbicide. Stem injection is very effective and recommended in areas where spraying herbicide is not feasible (e.g., in areas with desirable non-target plants). Approximately 2 to 5 milliliters of undiluted glyphosate-based herbicide (e.g., AquaMaster®) is delivered directly into the plant’s hollow stem between the 2nd and 3rd node from the soil surface (The Nature Conservancy 2019).

MNDR (2012a) summarizes the pros and cons of various recommended herbicides for controlling Japanese knotweed and presents details on adjuvants, concentrations, and timing details the of best practices in the MDNR factsheet in appendix B. See Soll (2004) for management practices and further information about herbicides and other specific information for stem injection methods.

Common Periw inkle (Vinca minor)

Periwinkle is a herbaceous vine that escaped cultivation and invades natural areas throughout the eastern US, growing in open to shady sites, including forests. It grows vegetatively by rhizomes that spread vigorously and forms dense mats, even under closed forest canopies. It can take over an understory and cover the forest floor, displacing native herbaceous and woody plants.

Common periwinkle can be removed by digging up the plants, but all roots must be removed to prevent resprouting. However, it is difficult to eradicate manually or mechanically because its weak stems often break before the root can be removed. With persistence, small patches can be removed manually when the ground is wet.

Because the plants stay green year-round, common periwinkle can be sprayed during the dormant season to avoid damaging surrounding vegetation. However, working with herbicides during cold temperatures is difficult, and snow cover could prevent treatment. The thick waxy cuticle that covers the leaves of periwinkle repels most water-based herbicides, so oil-based herbicides are recommended (e.g., triclopyr mixed with mineral oil at the strongest concentration suggested on the product label). Herbicide is an effective control, but applications need to be repeated for several seasons because plants resprout.

Woody Vines and Shrubs

Because of their similar biology and growth habit, many invasive woody vines and shrubs can be managed using comparable techniques. Manual digging or pulling can be effective in containing, suppressing, or locally eradicating early detections of invasive woody shrubs and vines when plants are in the seedling stage. Mechanical control should be performed as soon as the plants are large enough to grasp but before seed/fruit production. Plant stems should be dug up or pulled out by the base to ensure that the entire root system is removed. A digging or leverage tool can assist with plant removal. Disturbed soil should be tamped down firmly after removing plants. The woody plant material extracted from the ground can be mulched/chipped and left on-site or burned if allowed under local laws and regulations. The woody plants can also be arranged into brush piles for wildlife habitat (The Nature Conservancy 2019).

Cutting or mowing can be effective at containing or reducing small- to medium-sized infestations of invasive woody shrubs and vines. However, because dormant seeds in the soil are unaffected by this technique, cutting or mowing must be repeated for several years to reduce a population to desired levels.