Controlling Harding Grass in a
Grassland Setting
Stassia Samuels and Laura Julian
Redwood National and State Parks
Or, -this is our problem and how we
are dealing with it - we hope this
information will be useful to you
Thanks and Acknowledgements
Staff, partners, volunteers and interns who have supported this project:
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Dave Allen
Leonel Arguello
Jared Barr
Devin Bily
Chase Bodkin
Dan Boughter &
EPMT crew
Charles Brown
Denny Edmondson
Adam Erickson
Chad Greer
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Jennifer Hidalgo
Gary Hillier
Eric Hoff
Bradley Huffstedtler
Aidan Hutchens
Michael Insalaco
Laura Julian
Meagan Kavanaugh
Steven Krause
Amy Livingston
Amanda Mahaney
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Patrick Mulligan
Lizo Meyer
Josh Nauman
Scott Powell
Jean-Paul Ponte
Starr Ramos
Lindsay Scholl
Michael Shelley
Angela Swigart
Jenn Tiehm
Ryan Tietjen
Andrea Williams
Thanks and Acknowledgements
Funding for this project has been provided
from the following sources:
• The CA Exotic Plant Management Team – Bobbi Simpson
• NPS Pacific West Region natural resources program
• The California Department of Food and Agriculture
(CDFA)/Humboldt Co. Weed Mgmt. Area
• Redwood National and State Parks
Staffing partners have included:
• Student Conservation Association (SCA)
• Humboldt State University (HSU)
Rare Plants
– Howell’s montia CNPS 2
– Tracy’s tarplant CNPS 4
– California globe mallow
CNPS 1B
– Coast checkerbloom
CNPS 1B
Notable Wildlife
– Roosevelt elk
– Black bears
– Mountain lions
– Fishers
– Threatened Coho in
Redwood Creek
Harding grass, Phalaris aquatica
Project background
Problem definition
– Lands including the original Harding grass
infestation acquired in 1992
– Harding grass monoculture centered on stock
pond outflow
– Noticed spread in that and adjacent drainages in
early 2000’s
– Concerned about spread throughout BH if left
untreated
Project background
Challenges to treatment planning
• Didn’t know how much was out there, but
knew it was scattered throughout
approximately 2000 acres of prairie
• No experience with large scale herbicide
project
• Difficult to detect a single grass species in a
grassland setting (mapping and treatment)
• Short treatment window
• Funding limitations
Treatment Strategy
Gross Mapped and Treated
Acreage by Year
100.00
80.00
• Pilot (2005-6):
mapping, testing
feasibility of control
Gross Acres Mapped
Gross Acres Treated
• Phase I (2007-9): extensive mapping, treatment
of outliers and edges
• Phase II (2010-11): treatment of all known polys,
excluding the heart of darkness
• Phase III (2012-14): treatment of 90+% known
polys treated, incl. heart of darkness
• Phase IV (2015+): periodic maintenance
60.00
40.00
20.00
0.00
2005
2006
2007
2008
2009
2010
2011
2012
Treatment
Methods
Considered:
– Manual
– Mechanical
– Mechanical / chemical
– Chemical only
Chosen:
– Foliar spray of glyphosate formulation, 1.5%
herbicide (Aquamaster/ Aquaneat), .78% adjuvant
(Target Pro Spreader/Inlet)
Treatment – Labor
• Labor sources have included:
– Paid seasonal biological technicians
– Student Conservation Association (SCA) interns
– University students (wildlife, forestry, NR, range and
ecological restoration majors mostly, not so much
botany or biology)
– Volunteers
– Contractors
• Labor challenges have included
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–
–
Recruitment for short-term project
Training – grass ID and herbicide application
Morale and motivation
Contractors
Treatment – Logistics
Mapping/Monitoring
• Scale of project- large
• Frequency plots, photo points impractical
• Mapped every poly and
assigned cover class using
Trimbles and Garmins and our
home-grown database, that
crosswalks to WIMS etc
• Workers: given maps and GPS
units to find polys and
document new occurrences
• Significant effort but
worthwhile
• Consistency of mapper
important!
Intensive mapping allowed us to
answer two questions:
Where is the Harding grass?
Is our treatment working?
Harding Grass
Total Acreage by Year
2005, 2009 and 2012
By 2012 we think we have most of it mapped,
but undoubtedly have missed some
Results to date
Number of Mapped Polygons by Year
800
716
700
541
600
584
592
2010
2011
500
400
290
300
200
118
88
62
2005
2006
2007
100
0
2008
2009
2012
Results to date
Mapped Acreage by Year
100
86.98
90
71.36
80
70
76.10
75.59
60.59
60
43.23
50
40
30
21.81
20
10
8.75
28.19
18.85
18.36
16.07
23.29
21.36
11.30
9.08
0
2005
2006
2007
2008
Gross Acres Mapped
2009
2010
2011
Net Acres Mapped
2012
Results to date
Treated Acreage by Year
100
82.90
80
68.09
55.37
60
44.71
40.76
40
21.91
20
0
7.76
21.90
12.13
4.35
2.27
2006
2007
12.06
9.65
8.53
0
2005
2008
Gross Acres Treated
2009
2010
2011
Net Acres Treated
2012
So, are we reducing the cover of
Harding grass in the Bald Hills?
Results to date
% Cover of Harding Grass Over Time
Late Season Treatment vs. Early Season
90
80
70
60
50
40
30
20
10
0
81.18
44
0.72
Pre-treatment
Yr 1
Yr 2
Late Season Site (n=11 polys)
Early Season Site (n=10 polys)
7.1
Yr 3
Seasonality of Treatment
• Late season treatments appear to be more
effective in our ecosystem
• However, we were concerned that late season
treatment hinders our ability to limit seed
production
Lessons learned/bumps along the way
Seasonality of Treatment
• M. Shelley senior thesis confirms this
• If most plants we treat continue to produce
viable seed, how can we ever get ahead of it?
• Harding grass
seedlings are
poor competitors
35
30.5
Average seeds germinated
30
28.8
25
20
15
8.3
10
5
0
0.0
Early
Middle
Treatment
Late
Control
Treatment Hours and Cost
Per Gross and Net Acre
Treatment hours / cost per gross acre
Treatment hours/cost per net acre
78 hrs/ $1,554
64 hrs/$1,279
21 hrs/
$422
2008
14 hrs/
$279
2009
129 hrs/$2,579
71 hrs/$1,478
17 hrs/
$336
2010
35 hrs/$696
13 hrs/
11 hrs/
$265
$224
2011
2012
Moving Forward
• Post treatment vegetation succession
• Working with neighbors
• Maintenance mode by 2015?