**2007 Annual Report:**

**Perennial pepperweed Control Project**

![](media/image1.jpeg){width="1.05in" height="1.2527777777777778in"}

**Sarah Janson**

**Perennial Pepperweed Coordinator**

**Nancy Pau**

**Wildlife Biologist**

U.S. Fish and Wildlife Service

Parker River National Wildlife Refuge

6 Plum Island Turnpike

Newburyport, Massachusetts 01950

www.parkerriver.fws.gov

**INTRODUCTION**

Perennial pepperweed (*Lepidium latifolium*) is native to Eurasia. In
the 1930's the plant was introduced to the west coast of the United
States through a shipment of sugar beet seeds. Since that time,
pepperweed has become a serious problem on the west coast infiltrating
roadsides, riversides and pasture lands. Pepperweed is present in all
states west of the Rocky Mountains.

Although pepperweed was first recorded in Peabody, Massachusetts in 1924
and Norton, Connecticut in 1933, it has only recently been observed
spreading rapidly in Massachusetts and Connecticut. In New England,
infestations of *Lepidium latifolium* are mainly found near the coast
and on coastal islands. Stands often occur at the upper edges of salt
marshes above the high tide line, frequently forming dense stands. It
also occurs along highways, where it grows in disturbed areas near
roads. In 2006, pepperweed was confirmed in New Hampshire.

The state of Connecticut recently classified pepperweed as a noxious
weed. Without the natural checks on its growth which exist for
pepperweed in its native habitat, the plant has been growing and
spreading at an alarming pace in the United States. After only a few
seasons, a patch of pepperweed can grow into a dense, monoculture stand.
These stands are thick enough to shut out all light to the soil beneath
them and dominate water and nutrient supplies which prevents the growth
of native species. Pepperweed stands compete against native salt marsh
vegetation.

Perennial pepperweed is able to spread both vegetatively by rhizomes and
by seed. The root structure of pepperweed is extensive, penetrating at
least 60 cm into the soil. Root fragments as small as 2.5 cm are able to
re-sprout and grow into multi-stemmed plants. Pepperweed is a prolific
producer of seeds which can float though water ways and distribute on
the marsh surface.

Perennial pepperweed has been observed on the Parker River National
Wildlife Refuge since the 1990's. Four patches at the north end of the
refuge have been experimentally controlled in 2004 and 2005 with the
herbicide Escort. This work shows that applications of low concentration
Escort are an effective control for pepperweed in the Plum Island salt
marsh.

In 2006 the Refuge staff targeted Perennial Pepperweed throughout the
refuge and along and the Plum Island Turnpike to create a "fire break"
around the Refuge. All 46 known sites were treated on the Refuge and
nearly 5000 m­^2^ were cleared along the Turnpike. In 2007, recognizing
that pepperweed was spreading in the watershed through tidal movement,
the control project was expanded to map and treat Perennial Pepperweed
in Essex County including the towns of Salisbury, Newbury, Rowley,
Ipswich and Essex.

**METHODS**

[Permitting]{.underline}

In 2007 notices of intent were filed with Conservation Commissions in
Salisbury, Rowley, Ipswich and Essex. These towns granted permission to
work in wetland buffer zones to remove Pepperweed and apply herbicides.
We continued to work in Newbury under permission obtained in 2006. Once
permission was granted from town officials and landowners, off refuge
areas were mapped and added to a GIS database.

[Volunteer Recruitment]{.underline}

Working in partnership with Massachusetts Audubon Society, Plum Island
Kayaks, Parker River Clean Water Association and Ipswich Watershed
Association, we recruited volunteers for pepperweed removal through
schools, community networks, press releases, newspaper articles and word
of mouth. Two workshops were held in January 2007 to train volunteers to
identify pepperweed infestations from the previous year's dead growth.
These volunteers identified pepperweed sites in the expanded treatment
area. Nancy Pau gave a presentation to the Parker River Clean Water
Association to highlight the need to control pepperweed's spread through
riverways.

[Mapping and Site Identification]{.underline}

Volunteers were trained to identify perennial pepperweed by both its
dead winter stalks and in its growing stage. They chose quadrants of the
Great Marsh to search for pepperweed. Volunteers were encouraged to
begin the search at road crossings and culverts, and along the upper
edge of the marsh. Sites with pepperweed were marked on a paper map,
returned to the Parker River Office and added into a GIS database.

[Pulling]{.underline}

Volunteers were recruited and trained to assist with pepperweed pulling.
At sites selected for pulling, all visible pepperweed including bolting
stems and rosettes were removed by pulling out the stem with as much
root as possible. The first pulls were conducted between mid-May and
mid-August. All pulled sites were revisited in late August, and any
re-growth was pulled for a second time. Since pepperweed can easily
re-grow from small root fragments, we dried the pulled stems and roots
on a black top surface for at least 7 days. The dry stems and roots are
scheduled to be burned in winter 2008.

[Herbicide Application]{.underline}

For dense, monotypic stands on the Refuge, staff applied the herbicide
Escort, at 0.03% solution, via backpack sprayer in July and early August
while pepperweed was in flower. In an earlier pilot experiment, this
method was found to be 100% effective the first year and continued to
control pepperweed for 2-3 years after application.

**RESULTS & DISSCUSSION**

[Summary of Treatments]{.underline}

In 2006, 69 volunteers donated over 220 hours along with staff to
control pepperweed on the Plum Island Turnpike and on the Parker River
NWR. 5000 sq. m were cleared along the turnpike. On refuge property 46
sites were controlled, 31 by hand pulling and 15 with herbicide.

In 2007 81 volunteers donated over 250 hours to map and pull pepperweed
in the Great Marsh Region. After the winter mapping workshops in the
winter, volunteers identified 40 new pepperweed patches in Newburyport,
Newbury, Rowley, Ipswich and Essex. From May to August, volunteers
assembled to remove pepperweed from sites on the Refuge and in Newbury,
Ipswich and Essex. In 2007 we controlled Pepperweed on 8.5 ac. (Table 1)
creating nearly 1300 ac. of salt marsh free from pepperweed. 71 sites
were treated from Newbury to Essex: 38 by hand pulling and 33 with
herbicide.

  ------------------- ---------- ---------- -------------- ----------------
  Table 1. Summary of                                      
  Perennial                                                
  Pepperweed                                               
  treatment areas and                                      
  methods in Summer                                        
  2007.                                                    

                      Acres      Acres      Total Acres    Acres Free of
                      Pulled     Sprayed    Treated        Pepperweed

  Refuge Property     1.14       2.20       3.34           1091

  Newbury             1.88       2.60       4.48           142

  Ipswich             0.64       \--        0.64           14

  Essex               0.04       \--        0.04           30

  Total               3.70       4.80       8.50           1277
  ------------------- ---------- ---------- -------------- ----------------

In mid-August we accessed pepperweed sites from kayaks. 2 volunteers and
3 staff lead by a volunteer guide paddled down the Merrimac River from
Amesbury to Newburyport. From the water, several additional sites were
identified and pulled. Plum Island Kayaks of Newburyport donated the
kayaks for this program.

In 2007, 33 sites were treated with 0.03% Escort solution. At most sites
the herbicide was applied with backpack sprayers. Along the sides of the
Plum Island Turnpike, we were able to apply herbicide from truck mounted
sprayers.

An "Adopt-a-site" program took shape in 2007 with several volunteers
taking on pepperweed control on their property or neighborhood. These
include: Little Pine Island Road, sites on Old Point Road and Marsh
Avenue all in Newbury, MA.

[Efficacy of Treatment]{.underline}

Areas which were pulled in both 2006 and 2007 showed reduced amounts of
pepperweed in the second year (Table 2). Of the three sites where this
effort comparison was possible, 2 sites showed reduced work hours and
one site required the same number of hours. This indicates that hand
pulling is reducing pepperweed density and spread. On the refuge, 4
sites treated with herbicide in 2006 did not have pepperweed in 2007.
These sites will be closely monitored in 2008 for sprout from the
pepperweed seedbank.

  ------------------------ -------------- --------------- ---------------
  Table 2: Work hours                                     
  contributed to                                          
  Pepperweed control sites                                
  in Newbury over two                                     
  consecutive years.                                      

  Site                     Acres          Work Hours      

                                          2006            2007

  Littlefield & Town       1.10           12              6

  1^st^ Church             0.37           18              10

  Greenbelt                0.21           10              10
  ------------------------ -------------- --------------- ---------------

[Spread of Pepperweed]{.underline}

Since 2005 pepperweed has been mapped with GPS units on Refuge property.
The number of sites where pepperweed is monitored and treated on the
refuge has increased from 19 in 2005 to 47 in 2007 (Table 3). This
drastic increase in known sites also occurs on non-refuge lands. In 2007
mapping focused on easily accessible areas including the road edge while
2008 mapping will build on further exploration of previously mapped
areas and up-river areas. We strongly suspect that tidal influxes are
carrying pepperweed seeds up rivers and streams extending pepperweed
infestations.

  ------------ --------------------- ----------------- ---------------------
  Table 3.                                             
  Pepperweed                                           
  sites mapped                                         
  on Parker                                            
  River                                                
  National                                             
  Wildlife                                             
  Refuge from                                          
  2005 to                                              
  2007.                                                

  Year         Newly Mapped Sites    Total Sites       Sites treated and
                                     Monitored         free of Pepperweed

  2005         19                    19                \--

  2006         20                    39                0

  2007         8                     47                4
  ------------ --------------------- ----------------- ---------------------

Pepperweed found in rosette form late in the season may indicate that
the plants are growing from seed while bolting stem form may indicate
re-growth from a previous season or from root fragments. And while
Escort has proven 100% effecting in killing adult plants, continued
management of treated areas is necessary as the pepperweed seedbank may
sprout in years subsequent to treatment. Even in the treated areas where
pepperweed did not grow back in 2007 continued monitoring is warranted.

Overall, the Pepperweed Control Project demonstrates a positive effect
on controlling this invasive in the Great Marsh. Some sites are free
from pepperweed after one year of herbicide treatment and hand-pulled
sites are showing a reduction in stem number and density. These
encouraging results should motivate staff and volunteers as the project
continues.

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height="2.9965277777777777in"}

Ipswich high school students with the bags of pepperweed they pulled
from Town Farm Rd. in Ipswich.

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height="2.814583333333333in"}

Essex 5^th^ graders pulling at Conomo Point, Essex

  -------------------------------------------------- --------------------------- ---------------------------
  **[2007 Pepperweed Volunteers]{.smallcaps}**       **[Mapping]{.smallcaps}**   **[Pulling]{.smallcaps}**

  John Halloran, Kingston, NH                        X                           X

  Margot Hubbard, Rowley, MA                         X                           X

  Mark Jordan & Boy Scouts, Essex, MA                X                           X

  Jamie Krenn, Georgetown, MA                        X                           X

  Peter Phippen, Essex, MA                           X                           X

  Alex Pinto, Georgetown, MA                         X                           

  Cameron Smith Rapaport, Newburyport, MA            X                           

  Alfred & Amy Thurlow, Newbury, MA                  X                           X

  Peggy Duff & Girl Scouts, Troup 184, Essex, MA--5  X                           X
  members                                                                        

  Essex 5th grade class -- 40 students                                           X

  Ipswich High School --18 students                                              X

  Rick Keseli's UMass Boston Lab -- 4 members                                    X

  Betsy Clark, Byfield, MA                                                       X

  Pat Crowley, Newbury, MA                                                       X

  Kate deStadler, Newburyport, MA                                                X

  Barbara Kedesdy, Newbury, MA                                                   X

  Marilyn Kircus, Houston, TX                                                    X

  Lynette Leka, Newbury, MA                          X                           X

  John Outwater, Cambridge, MA                                                   X

  Eloise Schoeddner, Newbury, MA                                                 X

  Charlene Spaulding, Georgetown, MA                                             X

  Alfred & Amy Thurlow, Newbury, MA                  X                           X

  Jenna Wang, Cambridge, MA                                                      X
  -------------------------------------------------- --------------------------- ---------------------------