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ABSTRACT

HALL, KAREN RENAE. Alternative Management Techniques for Controlling Microstegium vimineum on Stream and Riparian Restoration Sites. (Under the direction of Dr. Douglas Frederick.)

Microstegium vimineum (Trin.) A. Camus, also known as Japanese stiltgrass, is an invasive grass native to Asia that has widely colonized riparian woodland and wetland

environments in the eastern U.S. Research was conducted on alternative management

techniques for M. vimineum control on stream and riparian restoration sites in field and greenhouse settings in North Carolina. Aquatic-use herbicides were applied preemergence

(PRE) and postemergence (POST) to M. vimineum populations that infested two stream restoration sites in the Piedmont and Upper Coastal Plain regions.

Herbicides applied PRE at standard recommended and lower than recommended

rates were evaluated in the field. Both rates of flumioxazin, fluridone, imazamox, and

imazapyr and the standard recommended rate of penoxsulam provided early reduction of

M. vimineum stem density 6 weeks after treatment (WAT) and extended control of plant biomass 30 WAT. Bispyribac, carfentrazone, and the lower rate of penoxsulam provided

effective stem reduction 6 WAT but not 30 WAT. Flumioxazin, fluridone, imazamox, and

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2010. Bispyribac, carfentrazone and penoxsulam provided good control at 6 WAT; results 30

WAT were mixed.

POST herbicide field trials showed standard recommended rates and lower than

recommended rates of diquat, flumioxazin, glyphosate, imazamox and imazapyr reduced

stem density of M. vimineum 6 WAT and plant biomass 30 WAT. Bispyribac, fluridone, and the low rate of glyphosate were less effective. Diquat, flumioxazin, glyphosate, imazamox,

and imazapyr significantly reduced M. vimineum plant cover 41 to 100% 6 WAT.

Flumioxazin, imazamox, and imazapyr reduced cover of the invasive weed 90 to 100% 30

WAT. Bispyribac, fluridone, and penoxsulam treatments provided varying control 6 and 30

WAT.

POST synthetic auxin herbicide field trials included 2,4-D, aminocyclopyrachlor,

aminopyralid, and triclopyr applied at 3 different rates to M. vimineum. Stem density was less in the herbicide treated plots compared to untreated control plots 6 WAT. Significant

vegetation cover reduction resulted from all application rates of aminocyclopyrachlor and

the highest rate of aminopyralid 6 WAT. Aminocyclopyrachlor applied at the higher levels

reduced M. vimineum between 83 to 100% 30 WAT.

Greenhouse studies evaluated effects of POST herbicides on M. vimineum and four native riparian graminoid species to determine if lower than recommended rates could

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Chasmanthium latifolium, Juncus effusus, and Panicum virgatum. Higher rates of diquat applications including 0.5 and 0.25 times recommended rate resulted in early leaf injury to

M. vimineum 1 WAT while glyphosate injury occurred later 6 WAT; all five treatment rates significantly reduced the invasive plant. P. virgatum was most susceptible to diquat injury at every rate, but only to glyphosate at the half-recommended rate. C. latifolium was

vulnerable to diquat injury 1 and 3 WAT, but showed signs of recovery 6 WAT.

Half-recommended rate of glyphosate was the only rate that significantly damaged this species.

C. vulpinoidea was effectively injured by diquat at half-recommended rates, but not at lower levels. Glyphosate-induced injury to C. vulpinoidea was significant at 0.5 and 0.25 recommended rates 6 WAT. Diquat applications to J. effusus resulted in sustained injury at the three highest rates throughout the three measuring periods. However, glyphosate

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Alternative Management Techniques for Controlling Microstegium vimineum on Stream and Riparian Restoration Sites

by

Karen Renae Hall

A dissertation submitted to the Graduate Faculty of North Carolina State University

in partial fulfillment of the requirements for the Degree of

Doctor of Philosophy

Forestry and Environmental Resources

Raleigh, North Carolina 2012

APPROVED BY:

____________________________ ____________________________ Douglas J. Frederick, Ph.D. Jean Spooner, Ph.D.

Chair of Advisory Committee

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Dedication

to

Hildred “Granny” Hall

This dissertation is dedicated in loving honor. You are forever my role model and

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Biography

Karen Renae Hall was born in Lenoir, North Carolina where she grew up and

graduated from Hibriten High School. After completion of a B.S. degree in Biology from the

University of North Carolina at Chapel Hill, Karen volunteered and worked for the U.S.

Forest Service in Chemult, Oregon as a wildlife biologist. Upon her return to North Carolina,

she enrolled in Dr. Richard Braham’s dendrology class and discovered she had a passion for

plants. Under the direction of Dr. Braham, she completed her M.S. degree in Forestry with a

minor in Botany at North Carolina State University. After a 2-year stint as a biologist in a

private engineering firm, Karen began her career as a riparian vegetation specialist for the

NCSU Water Quality Group in the Department of Biological and Agricultural Engineering.

She specialized in restoring vegetation on stream and wetland restoration projects

throughout the southeastern United States. Her position at NCSU was also an extension

appointment and she was involved in numerous outreach and education initiatives involving

vegetation in riparian settings throughout North Carolina. Through the encouragement of

her husband, her family, and Dr. Jean Spooner, Karen began the pursuit of her Ph.D. degree.

During her graduate career, Karen continued to work full time for NCSU as well as manage a

family that grew to include five children and numerous animals on her farm. She has been

inducted into Phi Kappa Phi (National Academic Honor Society), Gamma Sigma Delta (Honor

Society of Agriculture), and Xi Sigma Pi (National Forestry Honor Society). Karen has

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extension articles and organized regional stream restoration conferences. Karen plans to

continue her immediate Postdoctoral career in research and extension in the Biological and

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Acknowledgements

I would like to thank the numerous people who have helped and encouraged me

along this academic journey; this has truly been a team effort. First, I would like to

acknowledge Dr. Douglas Frederick who graciously agreed to serve as my committee chair

and provided valuable insights on my research. Dr. Jean Spooner deserves many thanks as

she constantly provided support and encouragement even in the toughest times. She has

been a great mentor, supervisor, and friend. I gratefully appreciate the wisdom imparted to

me by Dr. Greg Jennings during my graduate tenure; his enthusiasm for all aspects of

ecological restoration constantly inspires me. I owe many thanks to Dr. Rob Richardson for

his guidance and help with my research design as well as greenhouse and field trials.

Thanks to Steve Hoyle for always being there when I needed help with my herbicide

trials. Thanks also to Cody Hale, Jessica Scott, Evan Calloway, and Cody Smith for their help

in the greenhouse and laboratory. Morgan Hancock, Martin Hovis, Judah Emory, and Jessica

Blake braved the elements to assist in field trial setup; thank you all. Thanks to Morgan

Hancock for technical assistance with my photos. Thanks to Susan Sipal for editorial

assistance.

My husband, Norton Webster, has served as field guide, technician, lackey,

chauffeur, cheerleader, sounding board, and most importantly, friend. Without his love and

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were with me in the beginning of this journey and along the way came Lily, Wyatt, and Ellie.

I love and thank them all for being my biggest fans. Thanks to Rascal, my special field dog

who was with me at every site. Thanks also to my parents, Bill and Peggy Hall, as well as my

in-laws, Mary and Danny Webster, for taking care of my family and farm while I worked on

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Table of Contents

List of Tables ... xii

List of Figures ... xiv

Chapter 1. Research Purpose and Need ... 1

Stream and Riparian Restoration ... 2

Riparian Vegetation ... 4

Vegetation Functions ... 4

Vegetation Maintenance ... 8

Microstegium vimineum (Trin.) A. Camus ... 9

Background ... 9

Management and Control ... 11

Research Needs ... 15

Literature Cited ... 18

Chapter 2. Efficacy of Aquatic-Use Registered Herbicides for Preemergence Control of Microstegium vimineum on Stream and Riparian Restoration Sites ... 26

Introduction ... 29

Materials and Methods ... 33

Study Sites ... 33

Experimental Design ... 35

Data Collection ... 35

Data Analysis ... 36

Results ... 37

Stem Density and Dry Weight ... 37

Visual Percent Cover Evaluation ... 39

Discussion... 41

Sources of Materials ... 44

Acknowledgments... 45

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Chapter 3. Efficacy of Aquatic-Use Registered Herbicides for Postemergence Control of

Microstegium vimineum on Stream and Riparian Restoration Sites ... 53

Introduction ... 56

Materials and Methods ... 59

Study Sites ... 59

Experimental Design ... 61

Data Collection ... 61

Data Analysis ... 62

Results ... 63

Stem Density and Dry Weight ... 63

Visual Percent Cover Evaluation ... 65

Discussion... 67

Sources of Materials ... 69

Acknowledgments... 70

Literature Cited ... 71

Chapter 4. Efficacy of Synthetic Auxin Herbicides for Postemergence Control of Microstegium vimineum on Stream and Riparian Restoration Sites ... 78

Introduction ... 81

Materials and Methods ... 85

Study Sites ... 85

Experimental Design ... 87

Data Collection ... 88

Data Analysis ... 89

Results ... 89

Stem Density and Dry Weight ... 89

Visual Percent Cover Evaluation ... 90

Discussion... 93

Sources of Materials ... 96

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Literature Cited ... 97

Chapter 5. Evaluation of Low Glyphosate and Diquat Rates on the Exotic Invasive Grass Microstegium vimineum and Four Native Riparian Graminoids ... 108

Introduction ... 111

Materials and Methods ... 114

Results ... 116

Microstegium vimineum ... 116

Carex vulpinoidea ... 118

Chasmanthium latifolium ... 119

Juncus effusus ... 120

Panicum virgatum ... 121

Discussion... 123

Sources of Materials ... 126

Literature Cited ... 127

Chapter 6. Conclusions and Recommendations ... 141

Conclusions and Recommendations ... 142

Management of Microstegium vimineum Using Preemergence Herbicides ... 143

Management of Microstegium vimineum Using Postemergence Herbicides ... 145

Management of Microstegium vimineum Using Synthetic Auxin Herbicides ... 148

Management of Microstegium vimineum Using Low Glyphosate and Diquat Rates ... 150

Appendices ... 154

Appendix A-Site Maps ... 155

Appendix A1. Map of Beaver Dam Site (BDS). ... 156

Appendix A2. Map Yates Mill Site (YMS). ... 157

Appendix B-Chapter Two. Efficacy of Aquatic-Use Registered Herbicides for Preemergence Control of Microstegium vimineum on Stream and Riparian Restoration Sites: Supporting Data and Analysis ... 158

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Appendix B2. Chapter 2. Supporting statistical analysis of preemergence (PRE) control of Microstegium vimineum experimental trials ... 166 Appendix C-Chapter Three. Efficacy of Aquatic-Use Registered Herbicides for

Postemergence Control of Microstegium vimineum on Stream and Riparian Restoration Sites: Supporting Data and Analysis ... 182 Appendix C1. Chapter 3. Raw data of postemergence (POST) control of Microstegium

vimineum experimental trials. ... 183 Appendix C2. Chapter 3. Supporting statistical analysis of postemergence (POST) control of Microstegium vimineum trials. ... 190 Appendix D-Chapter Four. Efficacy of Synthetic Auxin Herbicides for Postemergence Control of Microstegium vimineum on Stream and Riparian Restoration Sites: Supporting Data and Analysis ... 208 Appendix D1. Chapter 4. Raw data of synthetic auxin postemergence (POST) control of Microstegium vimineum trials. ... 209 Appendix D2. Chapter 4. Supporting statistical analysis of synthetic auxin postemergence (POST) control of Microstegium vimineum trials. ... 213 Appendix E-Chapter Five. Evaluation of Low Glyphosate and Diquat Rates on the Exotic Invasive Grass Microstegium vimineum and Four Native Riparian Graminoids: Supporting Data and Analysis ... 233 Appendix E1. Chapter 5. Raw data of low rate diquat and glyphosate effects on

Microstegium vimineum experimental trials. ... 234 Appendix E2. Chapter 5. Supporting statistical analysis of low rate diquat and glyphosate effects on Microstegium vimineum experimental trials. ... 236 Appendix E3. Chapter 5. Raw data of low rate diquat and glyphosate effects on Carex

vulpinoidea experimental trials. ... 244 Appendix E4. Chapter 5. Supporting statistical analysis of low rate diquat and glyphosate effects on Carex vulpinoidea experimental trials. ... 247 Appendix E5. Chapter 5. Raw data of low rate diquat and glyphosate effects on

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List of Tables

Table 2.1. Mean Microstegium vimineum stem density and dry stem weight following preemergence herbicide applications 6 and 30 weeks after treatment (WAT) respectively; means from 2 separate years and 2 separate study sites in North Carolina. ... 49 Table 2.2. Mean Microstegium vimineum percent plant cover following preemergence

herbicide applications 6 and 30 weeks after treatment (WAT); means from 2

separate years and 2 separate study sites in North Carolina. ... 50 Table 3.1.Mean Microstegium vimineum stem density following postemergence herbicide

applications 6 weeks after treatment (WAT); means from 2 separate years and 2 separate study sites in North Carolina... 74 Table 3.2. Mean Microstegium vimineum dry stem weight response following

postemergence herbicide applications 30 weeks after treatment (WAT); means from 2 separate years and 2 separate study sites in North Carolina. ... 75 Table 3.3. Mean Microstegium vimineum percent plant cover following postemergence

herbicide applications 6 and 30 weeks after treatment (WAT); means from 2

separate years and 2 separate study sites in North Carolina. ... 76 Table 4.1 Mean Microstegium vimineum stem density following synthetic auxin herbicide

applications 6 weeks after treatment (WAT); means from 2 years and 2 study sites in North Carolina. ... 103 Table 4.2. Mean Microstegium vimineum dry stem weight following synthetic auxin

herbicide applications 30 weeks after treatment (WAT); means from 2 years and 2 study sites in North Carolina. ... 104 Table 4.3. Mean Microstegium vimineum plant cover following synthetic auxin herbicide

applications 6 weeks after treatment (WAT); means from 2 years and 2 study sites in North Carolina. ... 105 Table 4.4. Mean Microstegium vimineum plant cover following synthetic auxin herbicide

applications 30 weeks after treatment (WAT); means from 2 years and 2 study sites in North Carolina. ... 106 Table 5.1.Visualrating of vegetation mean response to various rates of diquat and

glyphosate in the greenhouse at 1 week after treatment. ... 132 Table 5.2.Visualrating of vegetation mean response to various rates of diquat and

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Table 5.3.Visualrating of vegetation mean response to various rates of diquat and

glyphosate in the greenhouse at 6 weeks after treatment. ... 134

Table 5.4.Mean dry weight vegetation response to various rates of diquat and glyphosate in the greenhouse at 6 weeks after treatment. ... 135

Table 5.5.Intercept, slope and coefficient of determination for Figure 5.1. ... 136

Table 5.6.Intercept, slope and coefficient of determination for Figure 5.2. ... 137

Table 5.7.Intercept, slope and coefficient of determination for Figure 5.3. ... 138

Table 5.8.Intercept, slope and coefficient of determination for Figure 5.4. ... 139

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List of Figures

Figure 2.1. Mean Microstegium vimineum dry weight response to preemergence herbicide applications 30 weeks after treatment. ... 51 Figure 2.2. Mean Microstegium vimineum plant cover response to preemergence herbicide

applications 30 weeks after treatment. ... 52 Figure 3.1. Mean Microstegium vimineum plant cover response to postemergence herbicide applications 6 weeks after treatment. ... 77 Figure 4.1. Mean Microstegium vimineum dry weight response to synthetic auxin herbicide

applications applied postemergence 30 weeks after treatment at Beaver Dam site (BDS) and Yates Mill site (YMS). ... 107 Figure 5.1. Effect of herbicide and application rates on Microstegium vimineum 1, 3, and 6

weeks after treatment (WAT). ... 136 Figure 5.2. Effect of herbicide and application rates on Carex vulpinoidea 1, 3, and 6 weeks

after treatment (WAT). ... 137 Figure 5.3. Effect of herbicide and application rates on Chasmanthium latifolium 1, 3, and 6

weeks after treatment (WAT). ... 138 Figure 5.4. Effect of herbicide and application rates on Juncus effusus 1, 3, and 6 weeks after

treatment (WAT). ... 139 Figure 5.5. Effect of herbicide and application rates on Panicum virgatum 1, 3, and 6 weeks

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Stream and Riparian Restoration

Throughout North Carolina and the southeastern United States, restoration of

degraded stream channels and riparian buffers has flourished in recent years. Initiatives to

improve surface water quality have been driven by federal, state, and local programs

ranging from voluntary actions by individual landowners to compensatory mitigation

projects that offset various impacts such as development and road construction (Bernhardt

et al., 2005; CWMTF, 2011; Hough and Robertson, 2009; Lave et al., 2008; NCDENR, 2011;

NCDWQ, 2011; Sudduth et al., 2007). Generally the goals of stream and riparian area

restoration are to aid in the recovery of degraded, damaged or destroyed ecosystems and

reestablish self-sustaining functional ecosystems (Society for Ecological Restoration

International Science & Policy Working Group, 2004).

Restoration projects driven by mitigation are often mandated to restore ecosystems

to “natural conditions” based on historical data or relatively unaltered reference areas. The

SER International Primer on Ecological Restoration (Society for Ecological Restoration

International Science & Policy Working Group, 2004) states that a restored ecosystem

contains characteristic populations of species found in the reference ecosystems and that

these species are indigenous to the greatest practicable extent. Further, ecological

restoration projects should be as self-sustaining as the reference sites and should

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As a result, many state and local government agencies have adopted natural channel

design techniques to restore and rehabilitate unstable streams and degraded riparian areas.

This holistic approach to stream restoration encompasses a broad range of measures,

including the identification and removal of the watershed disturbances that are causing the

impairments, installation of in-stream structures and planting of native vegetation to

protect streambanks from erosion, creation of aquatic and terrestrial habitat, and the

reshaping or replacement of unstable stream reaches into appropriately designed

functional streams and associated floodplains (Doll et al., 2003). With this approach, the

channel restoration design is based largely on stable reference reach streams which

maintain their dimension, pattern and profile over time (Rosgen, 1996).

Restoration of riparian buffers also relies on the use of reference ecosystems as well

as other sources of information during the planning and design phases. Though many

practitioners design for a pristine historical riparian condition, planning for natural

authenticity rather than historical accuracy is a more realistic objective for ecosystem

restoration and choosing an appropriate reference site is of tantamount importance for

both designing and comparing the restoration project (Clewell, 2000). Acknowledging that

reference sites may be in a different successional state than that of the final desired

restoration state and that non-native invasive species have increased in most river systems

over time (Hughes et al., 2005), existing information such as ecological descriptions, species

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(Society for Ecological Restoration International Science & Policy Working Group, 2004) can

be beneficial in the riparian restoration design. Also, field assessments and site inventories

of biota can reveal remnant desired populations and conditions (Matthews et al., 2011).

Reference areas may be found upstream and downstream of the proposed restoration site

as well as in adjacent drainages (Sieben and Reinecke, 2008). Regional guidebooks may

provide generalized information that can be utilized.

Riparian Vegetation

Vegetation Functions

The importance of vegetation in stream and riparian restoration projects cannot be

overstated. Riparian areas have some of the most diverse and complicated biota of all

ecosystems (Gregory et al., 1991; Naiman and Decamps, 1997) due to dynamic interactions

of fluvial hydrology and variable terrestrial topography and soils within the floodplain.

Vegetation and fluvial processes have co-evolved to create a natural system that depends

on the other for its proper functioning (Millar, 2000; Osterkamp and Hupp, 2010). Riparian

vegetation is frequently disturbed by floods that not only transport sediment and debris but

also seeds and plant propagules of various species. Seasonal inundation of floodplains as

well as large sediment deposits from major flooding events can create a challenging

environment for vegetation to establish and grow. Yet, plant species richness in these

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Some researchers (Naiman et al., 1993) account for this richness by 1) the intensity and

frequency of flood events; 2) variations in topography and soil due to lateral movement of

fluvial channels; 3) climate variations as streams flow from high to low altitudes; and 4)

disturbance as a result of activity in the upland areas.

Much literature exists on the importance of vegetation to the fluvial systems.

Vegetation along stream banks helps to regulate light infiltration and surface water

temperature (DeWalle, 2008; DeWalle, 2010; Sweeney, 1993). Inputs of native plant leaf

litter and dissolved organic matter support benthic macroinvertebrates and other

microorganisms which in turn serve as an important food source for fish populations (Graça,

2001; Kominoski and Pringle, 2009; Wallace and Webster, 1996). Large woody debris are

important to fish and benthic macroinvertebrate habitat (Gregory et al., 1991; Ogren and

King, 2008; Opperman and Merenlender, 2004). Riparian plants serve to uptake nutrients

and filter pollutants (Chambers et al., 2004; Hill, 1996; Peterjohn and Correll, 1984;

Sweeney et al., 2004; Vidon et al., 2010). Forests along rivers and streams are critical faunal

migration corridors (Alexander et al., 2011; Meyer et al., 2007; Perault and Lomolino, 2000)

and provide food, refuge, and breeding grounds for numerous organisms (Crawford and

Semlitsch, 2007; Smith and Racey, 2008; Sullivan and Vierling, 2009). Complex layers of

vegetation help to slow water flow and trap sediment during flooding events (Gurnell, 1997;

Hupp, 2000; Nilsson and Svedmark, 2002; Steiger et al., 2003). Soil particles along the

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fine and large roots from a variety of riparian plant species (Abernethy and Rutherfurd,

2000; Bochet et al., 2005; Bubenzer and Mamo, 2001; Lyons et al., 2000; Micheli et al.,

2004; Wynn et al., 2004).

This last point is of particular importance in channel restoration. As watersheds

change and degrade through natural and anthropogenic activities, stream bank stability can

become compromised. Riparian vegetation along the banks of channels can increase the

stability of the sediment particles reducing near-bank velocity and shear stress, increasing

overall bank strength through root mass networks that bind soil particles, and enhancing

interstitial sediment deposition of fine particles (Millar, 2000; Simon and Collison, 2002).

Vegetation also can increase the banks of stream channels by intercepting rainfall

throughout the canopy before it reaches the soil and by extracting soil moisture through

evapotranspiration (Simon and Collison, 2002). A study on British Columbia river bends

showed that non-vegetated meander bends were five times more likely to experience

erosion than vegetated bends (Beeson and Doyle, 1995). Type of vegetation, however,

matters in reducing erosional forces. Herbaceous vegetation has smaller, finer, and more

numerous roots than that of woody vegetation. Wynn et al. (1994) found that woody

vegetation in riparian areas in Virginia had greater volume and length of larger diameter

roots below 15 centimeters. The study also showed that woody plant roots were more

widely distributed over the channel bank face likely affording more protection to soil

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small number of large roots rather than numerous small roots. As a result, woody

vegetation may be more important in management of steep bank slopes (Wynn et al.,

2004).

Planting native woody riparian vegetation in stream and riparian restoration sites is

a widely used technique in the overall practice of natural channel design. Forbs and grasses

do however play an important role in stream and riparian restoration projects. Grass buffer

strips have been shown extensively to trap sediment and help prevent increased sediment

loading in surface waters (Carline and Walsh, 2007). Several studies have shown the

contributions that native grasses in particular make to streambank stability (Lyons et al.,

2000; Simon and Collison, 2002). Panicum virgatum L. (switchgrass) has been demonstrated to have a very strong root network due to a high root area ratio and roots that extend deep

into the soil horizon compared to other grasses (Simon and Collison, 2002). In practice,

temporary, annual grasses should be planted immediately following construction activities

to establish cover and prevent elongated exposure of bare soil. Permanent native

herbaceous species are often planted in addition to trees and shrubs in order to more

quickly create living root mass while the slower-growing woody plants become established

(NCDENR, 2009). A combination of different native planting regimes is becoming more of a

recommended practice for stream and riparian restoration projects (Doll et al., 2003;

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8 Vegetation Maintenance

Depending on the overall goals and objectives of the project, maintenance is usually

recommended for each restoration site to assure the successful establishment of planted

vegetation (Doll et al., 2003; Eubanks, 2004). Yet many restoration sites are infested with

invasive exotic vegetation that is adapted to highly disturbed environments such as

floodplains. Riparian areas are prone to invasions of aggressive plant species due to the

highly dynamic hydrologic regime (Planty-Tabacchi et al., 1996; Tickner et al., 2001). In

areas where natural conditions are desired, invasive species can hinder restoration efforts

(D'Antonio and Meyerson, 2002; Oswalt et al., 2004). Nonnative vegetation can invade and

impact natural communities by reducing the abundance and the diversity of native plants

(Burton et al., 2005; Fierke and Kauffman, 2006; Gorchov and Trisel, 2003).

Resource managers can benefit from having a management plan for controlling

invasive riparian plants prior to and following restoration efforts (Shafroth et al., 2008).

Invasive or nuisance plant management is an important component of stream and riparian

restoration efforts (Munro, 2006). Each invasive species has its own life history and

establishment characteristics, therefore management plans should address each one

separately with highest priority of control given to species that pose the greatest threat to

the restored ecosystem (Society for Ecological Restoration International Science & Policy

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and pose a threat to local and regional ecosystems. One such plant is Microstegium vimineum.

Microstegium vimineum

(Trin.) A. Camus

Background

Microstegium vimineum (Trin.) A. Camus, also known as Japanese stiltgrass,

Nepalese browntop, and annual jewgrass, is an annual C4 grass native to lowlands and low

mountains in Asian countries such as Japan, China, India, Malaysia, Korea, Sri Lanka and

Pakistan (Ohwi, 1965; Tu, 2000). M. vimineum was first accounted for in the United States around Knoxville Tennessee in 1919 (Fairbrothers and Gray, 1972), most likely entering the

country through import as packing material for porcelain from China (Tu, 2000). Unlike

other C4 plants, M. vimineum is shade-tolerant and well-adapted to low-light environments (Horton and Neufeld, 1998; Winter et al., 1982). It is highly competitive with native

vegetation and once established, it frequently forms a dense, self-perpetuating

monoculture that suppresses other vegetation and negatively affects native plant species’

richness and diversity (Adams and Engelhardt, 2009; Barden, 1987; Judge et al., 2008;

Loewenstein and Loewenstein, 2005; Vidra et al., 2006). An individual plant can produce as

many as 1000 seeds which can remain viable in the soil up to five years (Barden, 1987; Tu,

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and sunlight strengthens its competitiveness and invasibility in riparian habitats (Cheplick,

2005; Claridge and Franklin, 2002; Williams, 1998).

This plant has colonized a variety of sites, including disturbed sites in moist soils,

especially stream and river floodplains throughout the 24 eastern U.S. states, Washington

D.C. and Puerto Rico (Barden, 1987; Fairbrothers and Gray, 1972; Matthews et al., 2011;

USDA NRCS, 2011; Warren et al., 2011). Barden (1987) showed that this exotic plant readily

invaded disturbed areas in a North Carolina floodplain much more quickly than established

areas. Because M. vimineum seeds float, floods can easily distribute them throughout riparian areas (Mehrhoff, 2000; Warren et al., 2011). Litter and soil disturbances help to

facilitate greater invasions of the nuisance species (Marshall and Buckley, 2008), particularly

those disturbances created by human activities (Rauschert et al., 2010). Recent efforts to

restore streams and riparian areas throughout the eastern United States have resulted in

large areas of disturbed floodplains allowing M. vimineum to invade and dominate these sites (Barbara Doll-pers. comm.). This can be a major setback in the establishment of

naturally regenerating as well as planted vegetation on the restoration site. For example,

Oswalt et al. (2004) found that first-year growth of Quercus rubra L. (northern red oak) seedlings planted along an intermittent stream in southwest Tennessee was impeded by a

large population of M. vimineum as compared to seedling growth in areas without the invasive plant. In another study, Leersia virginica Willd. (whitegrass), Carex radiata

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native graminoids in riparian ecosystems, produced less biomass when invaded by

Microstegium (Flory et al., 2007). Further, soil amelioration practices to enhance the growth of planted species on restoration sites can benefit the exotic species inadvertently. A

seedbank study of a bottomland hardwood site in central North Carolina demonstrated a

substantial increase in number of stems and biomass of M. vimineum with the addition of fertilizer (McGrain, 1993). Yet, with control and management of this invader, natural

ecosystems can recover (Flory and Clay, 2009).

Management and Control

Environmentally sensitive ecosystems such as streams, wetlands, and riparian areas

require special consideration when forming management plans to control invasive exotic

weeds. Native flora and fauna protection should be taken into account (Flory, 2010; Going

and Dudley, 2008; Simao et al., 2010), especially in restoration projects that emulate natural

conditions. Variations in topography, hydrology, and soil conditions can create a diverse and

complicated ecosystem that demands individual maintenance prescriptions following

restoration efforts. M. vimineum invasions can challenge practitioners in their

recommendations of control for this species. Because of its ability to grow in a variety of

conditions, different control techniques may have to be employed on the same restoration

site. Additionally, though this is an annual grass species, recruitment of new seedlings from

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management is necessary to deplete the soil seed bank (Tu, 2000) and long-term

monitoring and maintenance may be needed.

Manual and mechanical control mechanisms of M. vimineum include hand pulling, mowing, and controlled burns. Several studies have examined the efficacy of hand pulling,

particularly as it applies to native plant composition and recovery in sensitive environments

(Flory, 2010; Flory and Lewis, 2009; Judge et al., 2008). The Nature Conservancy

recommends hand pulling as the preferred method of extraction because “it is highly

specific and provides minimal impact” to the areas of infestation (Tu, 2000). It is recognized

that timing is essential and that removal by this method should take place late in the season

before seeds are shed from the plants. Pulling too early will allow germination of new M. vimineum seedlings from the seed bank to colonize the newly exposed area. Yet Flory (2010) found that even after two years of removing M. vimineum by hand the site was invaded the following spring by the exotic plant. Further, hand pulling any weed is time and

labor intensive. On large restoration sites, this is neither practical nor economical.

Mowing or weed trimming is also a recommended control method in the late

summer before seed production (Tu, 2000). Several studies have shown a reduction in M. vimineum biomass compared to reference plots after a fall mowing with a mechanical string trimmer (Flory and Lewis, 2009; Judge et al., 2008). However these methods also can be

costly and time consuming. Further, string trimmers can damage newly planted tree

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summer applications (Barden, 1987; Flory and Lewis, 2009), though prescribed burning in a

forest in southeast Ohio actually increased establishment of M. vimineum (Glasgow and Matlack, 2007). In practice, fire is not a practical management tool in very many settings,

especially restoration sites that are seasonally wet or are located in populated areas.

Studies on biological controls for M. vimineum have been limited. White-tail deer herbivory is rare as the plant is not a preferable browse food for the ungulates (Webster et

al., 2008). Some native invertebrates derive a portion of their biomass carbon from the

exotic plant through “chewing” and “sucking” (Bradford et al., 2010). In its native range,

twelve fungal pathogens and eight arthropods are known to exist as natural enemies (Zheng

et al., 2004). In 2009, however, a fungus was discovered on field populations of M. vimineum growing in Arnoldsburg, West Virginia (Kleczewski and Flory, 2010). Plants developed dark, necrotic lesions that preceded death of the plant. Kleczewski and Flory

(2010) identified the pathogen on sample leaf material as Bipolaris sp., a fungal pathogen similar to Bipolaris zeicola (G. L. Stout) Shoemaker which causes leaf spot of maize. Further greenhouse studies showed the fungus caused delayed flowering and reduced seed head

production of the invasive plant. More research is needed to determine if this fungus can be

utilized as a biological control.

Chemical control, i.e. herbicides, have been researched and applied on M. vimineum for a number of years by several researchers (Flory, 2010; Gover et al., 2002; Gover et al.,

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herbicides, including pendimethalin, benefin plus oryzalin, dithiopyr, isoxaben plus

trifluralin, oryzalin, oxadiazon, prodiamine, and trifluralin, have been used successfully to

control M. vimineum populations (Flory, 2010; Gover et al., 2003; Judge et al., 2005a). Postemergence (POST) control herbicides that have shown effectiveness are fenoxaprop-P,

fluazifop-P, glyphosate, glufosinate, imazapic, and sethoxydim (Flory, 2010; Jones et al.,

2004; Judge et al., 2005b; Judge et al., 2008; Peskin, 2005).

At present, no known research has been performed specifically on aquatic-use

herbicides for M. vimineum control. Federal and some state laws require that any

herbicides used in, on, or over water must have an aquatic registration due to the fact that

herbicides used in an aquatic setting can spread more widely via water and can result in

greater environmental exposure. Because M. vimineum frequently occurs in riparian aquatic and semi-aquatic areas, including stream banks and riparian wetlands, aquatic-use

herbicides would be required in these ecosystems. This research assesses efficacies of

herbicides registered and pending registration for aquatic use applied both PRE and POST

on M. vimineum populations in the riparian setting.

Densely planting native species to effectively outcompete exotic species for

resources is a possible control technique. Though there is little known information on using

native vegetation to control M. vimineum populations (though see Cole and Weltzin, 2005), other studies have shown success by employing such techniques (Booth et al., 2003;

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studied and used on stream restoration projects due to its soil stabilizing root system and

tall clumping habit that captures sediment (Simon and Collison, 2002). Anecdotal evidence

from past stream restoration projects (Hall-personal observation) has revealed that P. virgatum and Juncus effusus L. (soft rush), when planted in dense quantities in disturbed open areas, has prevented the spread of M. vimineum into these areas. Additional

graminoid species commonly planted on restoration sites may also be of benefit. A portion

of this research will address the effects of low herbicide application rates on native

graminoids species and M. vimineum.

Research Needs

Given the numerous stream and riparian area restorations taking place in the

Southeast and in North Carolina, invasive plant control is important for successful

establishment of native vegetation on these sites. Alternative management methods are

needed to control M. vimineum on restoration sites. This research focuses on the management of this troublesome weed which thrives in these streamside settings.

In projects that either have or potentially will have large infestations of the invasive

M. vimineum, herbicides may be the most practical and economical treatment method. The effectiveness of herbicides registered for aquatic use on this invasive plant has yet to be

studied in depth; therefore this study tests the hypothesis that aquatic-use herbicides will

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optimum rate and time to produce the greatest control over M. vimineum in these riparian environments without negatively impacting native vegetation. Specifically, this research

project evaluates the efficacy of herbicides registered for aquatic use and herbicides with

pending aquatic-use registrations applied at various rates for both preemergence (PRE) and

postemergence (POST) control of M. vimineum and their effects on desirable native riparian vegetation. In Chapters 2 and 3, data and analyses are presented for efficacies of

aquatic-use herbicides applied PRE and POST, respectively, on M. vimineum populations infesting two stream and riparian restoration sites in North Carolina. Chapter 4 provides results of

field trials testing the efficacies of synthetic auxin herbicides applied POST on small seedling

M. vimineum plants located on two restoration sites in North Carolina. In Chapter 5, results are presented from greenhouse studies determining the efficacies of low glyphosate and

diquat rates applied POST for control of M. vimineum as well asevaluation of these same herbicides on desirable riparian graminoids that includes J. effusus, P.virgatum, Carex vulpinoidea Michx. (fox sedge), and Chasmanthiumlatifolium (Michx.) Yates (river oats). Lastly, Chapter 6 follows up with overall conclusions from all research trials and

recommendations for stream and riparian restorationists dealing with infestations of M. vimineum on restoration sites.

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restoration projects. This study will lay the foundation for continued research in

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Chapter 2.

Efficacy of Aquatic-Use Registered Herbicides for Preemergence

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Efficacy of Aquatic-Use Registered Herbicides Used for Preemergence Control

of

Microstegium vimineum

on Stream and Riparian Restoration Sites

Karen R. Hall, Robert J. Richardson, Jean Spooner, Steve T. Hoyle and Douglas J Frederick*

Microstegium vimineum is an invasive, nonnative grass introduced from Asia that has now spread throughout riparian areas of the eastern United States. Preemergence (PRE)

herbicides registered for aquatic use were evaluated for control of Microstegium vimineum at standard recommended and lower than recommended rates on two separate stream and

floodplain restoration sites in the Piedmont and Upper Coastal Plain of North Carolina. Both

rates of flumioxazin, fluridone, imazamox, and imazapyr and the standard recommended

rate of penoxsulam provided early reduction of M. vimineum stem density 6 weeks after treatment (WAT) and extended control of plant biomass throughout the growing season 30

WAT. Bispyribac, carfentrazone, and lower rates of penoxsulam also provided effective

stem reduction 6 WAT but no biomass reduction 30 WAT. Visual ratings of weed control

showed flumioxazin, fluridone, imazamox, and imazapyr controlled 98 to 100% of M. vimineum 6 WAT. Visual ratings of these same treatments 30 WAT demonstrated 86 to 97% control in 2009 and 92 to 100% control in 2010. Bispyribac, carfentrazone and penoxsulam

*

First and third authors: Extension Associate and Extension Professor,Department of Biological and

Agricultural Engineering. North Carolina State University, Raleigh, NC, 27695-7637; Second and fourth authors:

Assistant Professor and Research Specialist,Department of Crop Science. North Carolina State University,

Raleigh, NC, 27695-7620; Fifth author: Professor,Department of Forestry and Environmental Resources. North

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applications 6 WAT resulted in greater plant control compared to the untreated plots, but

had mixed control results 30 WAT. Based on these results, PRE application of lower than

recommended rates of flumioxazin, fluridone, imazamox and imazapyr as well as the

standard recommended rate of penoxsulam can effectively control M. vimineum on stream and riparian restoration sites.

Nomenclature: Bispyribac; carfentrazone; flumioxazin; fluridone; imazamox; imazapyr; penoxsulam; glyphosate; Japanese stiltgrass, Microstegium vimineum (Trin.) A. Camus

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Introduction

Throughout the United States, stream and riparian restoration projects are being

undertaken in efforts to improve water quality. The goals of these restorations are to aid in

the recovery of degraded, damaged or destroyed ecosystems and to reestablish

self-sustaining functional ecosystems (Society for Ecological Restoration International Science &

Policy Working Group, 2004). Yet many restoration sites have become infested with invasive

exotic vegetation that is adapted to highly disturbed environments such as floodplains.

Riparian areas are prone to invasions of aggressive plant species due to the highly dynamic

hydrologic regime (Planty-Tabacchi et al., 1996; Tickner et al., 2001). In areas where natural

conditions are desired, invasive species can hinder restoration efforts (D'Antonio and

Meyerson, 2002; Oswalt et al., 2004). Nonnative vegetation can invade and impact natural

communities by reducing the abundance and the diversity of native plants (Burton et al.,

2005; Fierke and Kauffman, 2006; Gorchov and Trisel, 2003). Invasive exotic plants that are

highly mobile and pose a threat to local and regional ecosystems are of greatest concern

and should be given highest priority of control in restoration management plans (Society for

Ecological Restoration International Science & Policy Working Group, 2004).

Microstegium vimineum (Trin.) A. Camus, also known as Japanese stiltgrass,

Nepalese browntop, and annual jewgrass is a problematic exotic plant in the eastern United

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countries such as Japan, China, India, Malaysia, Korea, Sri Lanka and Pakistan (Ohwi, 1965;

Tu, 2000). M. vimineum was first accounted for in the United States around Knoxville Tennessee in 1919 (Fairbrothers and Gray, 1972), most likely through import as packing

material for porcelain from China (Tu, 2000). This plant has since colonized a variety of sites,

including disturbed areas in moist soils, especially stream and river floodplains throughout

24 eastern U.S. states, Washington D.C. and Puerto Rico (Barden, 1987; Fairbrothers and

Gray, 1972; Matthews et al., 2011; USDA NRCS, 2011; Warren et al., 2011). The successful

dominance of M. vimineum is due in part to its plasticity under varying environmental conditions such as soil nutrients and sunlight (Cheplick, 2005; Claridge and Franklin, 2002;

Williams, 1998). This speciesis shade tolerant and well adapted to low-light environments

(Horton and Neufeld, 1998; Winter et al., 1982). Furthermore an individual plant can

produce as many as 1000 seeds which can remain viable in the soil up to five years (Barden,

1987; Tu, 2000). As a result of M. vimineum’s adaptability, it is highly competitive with native vegetation and once established, it frequently forms a dense, self-perpetuating

monoculture that suppresses other vegetation and negatively affects native plant species

richness and diversity (Adams and Engelhardt, 2009; Barden, 1987; Judge et al., 2008;

Loewenstein and Loewenstein, 2005; Vidra et al., 2006). An opportunistic invader of

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Environmentally sensitive ecosystems such as streams, wetlands, and riparian areas

require special consideration when treating M. vimineum. Variations in topography,

hydrology, and soil conditions can create a diverse and complicated ecosystem. Native flora

and fauna protection should be taken into account when treating this invasive plant (Flory,

2010; Going and Dudley, 2008; Simao et al., 2010), especially in restoration projects that

emulate natural conditions. Several studies have examined the efficacy of hand pulling this

weed, particularly as it applies to native plant composition and recovery in sensitive

environments (Flory, 2010; Flory and Lewis, 2009; Judge et al., 2008). Yet Flory (2010) found

that even after two years of removing M. vimineum by hand, the site was reinvaded the following spring by the exotic plant. Several studies have shown a reduction in M. vimineum biomass compared to reference plots after a fall mowing with a mechanical string trimmer

(Flory and Lewis, 2009; Judge et al., 2008). Prescribed burning has also been shown

effective in late summer applications (Barden, 1987; Flory and Lewis, 2009), though

prescribed burning in a forest in southeast Ohio actually increased establishment of M. vimineum (Glasgow and Matlack, 2007). Many of these methods however are costly, labor intensive and time consuming. Further, given the large size of some riparian restoration

sites, a more practical and efficient control method is needed.

Reduction of M. vimineum seed banks is crucial to any restoration project aiming to return these infested ecosystems to a more natural and functioning state. Controlling the

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impacts to existing native vegetation can be minimized. Chemical control of this invader has

been studied by several researchers (Flory, 2010; Gover et al., 2002; Gover et al., 2003;

Jones et al., 2004; Judge et al., 2005b; Judge et al., 2008). Preemergence (PRE) herbicides,

including pendimethalin, benefin plus oryzalin, dithiopyr, isoxaben plus trifluralin, oryzalin,

oxadiazon, prodiamine, and trifluralin, have controlled M. vimineum populations (Flory, 2010; Gover et al., 2003; Judge et al., 2005a). However, none of these herbicides are

approved for aquatic use and given that M. vimineum can often occur along stream banks and in riparian wetlands, these chemicals would not be appropriate for invasive plant

treatment in aquatic and semi-aquatic settings.

At present, no known research has been performed specifically on aquatic-use

herbicides for PRE M. vimineum control. Federal and state laws require that any herbicides used in, on, or over water must have an aquatic registration because herbicides used in an

aquatic setting can spread more widely via water and can result in greater environmental

exposure. Because M. vimineum frequently occurs in riparian aquatic and semi-aquatic areas, herbicides registered for aquatic use would be required in these ecosystems. This

study tests the hypothesis that aquatic-use herbicides applied preemergence will effectively

control M. vimineum on two restored stream and floodplain sites in North Carolina. Specifically, the objectives of this research include: (1) assessing efficacies of various PRE

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herbicides and determining if lower than recommended rates are effective; and (3)

determining effectiveness of herbicides on M. vimineum 6 and 30 weeks after treatment (WAT).

Materials and Methods

Study Sites. The field experiments were conducted in 2009 and 2010 at two locations in

central North Carolina on recent stream and floodplain restoration projects. The first site

was located along a Piedmont stream in Wake County on North Carolina Department of

Agriculture property and is referred to as the Yates Mill Site (YMS). The second site, known

as the Beaver Dam Site (BDS) was located in an Upper Coastal Plain riparian area in Harnett

County on private land.

The Piedmont site is a stream and floodplain restoration project that was completed

in the spring of 2002. A tributary to Steep Hill Creek, Yates Mill Tributary 1a was the site of a

stream restoration project based on a Priority I natural channel design approach for an

incised stream (Rosgen, 1997). This restoration utilized natural channel design procedures

to restore an incised, straightened stream’s dimension, pattern and profile. Prior to

restoration construction, this area was a mature forest with a mixed hardwood and pine

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consisted of Toxicodendron radicans (L.) Kuntze (poison ivy), though M. vimineum was present in small scattered patches throughout the floodplain. Restoration activities resulted

in a disturbed open swath of floodplain approximately 50-meters wide. Following

construction, woody trees and shrubs were planted throughout the floodplain in the fall of

2002. Surveys the following summer revealed the post-construction riparian area

completely covered in M. vimineum. Though the woody stems were surviving, it was observed that very few low-growing herbaceous species other than M. vimineum were present.

The Upper Coastal Plain site contained a tributary that was also restored with a

Priority I technique in the fall of 2007. The riparian area consisted of a mature bottomland

forest including overstory trees such as L. styraciflua, P. taeda, and Celtis laevigata Willd. (sugarberry). A sparse shrub midstory included L. benzoin, A. serrulata, Arundinaria gigantea (Walter) Muhl. (giant cane), and Callicarpa americana L. (beautyberry). M. vimineum was present in small scattered areas prior to construction. Large trees were intentionally avoided during restoration activities, yet construction disturbed an area

approximately 30 meters on each side of t

Figure

Table 2.1. Mean Microstegium vimineum stem density and dry stem weight following preemergence herbicide applications 6 and 30 weeks after treatment (WAT) respectively; means from 2 separate years and 2 separate study sites in North Carolina
Table 2.2. Mean Microstegium vimineumafter treatment (WAT); means from 2 separate years and 2 separate study sites in North Carolina
Figure 2.1. Mean Microstegium vimineum dry weight response to preemergence herbicide applications 30 weeks after treatment
Figure 2.2. Mean Microstegium vimineum plant cover response to preemergence herbicide applications 30 weeks after treatment
+7

References

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