Japanese Knotweed Control

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Japanese Knotweed Control:
It Takes a Community
Leslie Kuhn
Field Projects Coordinator
Mid-Michigan Stewardship Initiative
[email protected]
Mid-Michigan Stewardship Initiative (MMSI)
• The Mid-Michigan chapter of the
Stewardship Network
• Brings together volunteers,
professionals, landowners, and public
agencies to restore natural areas
• We focus on invasive
species control and
community outreach
on invasive species
• We also create
native plant
demonstration gardens
Knotweed Team:
Laurie Kaufman,
Jim Hewitt, Billy Hartill,
Pat Witte, Leslie Kuhn,
and volunteers
MMSI Planning Committee meeting
at Ingham County Parks
Japanese Knotweed (Fallopia japonica)
• Introduced from Asia as an
ornamental in mid-1800’s
• Flowers in late summer
• Known invasive in US by 1900
• Reddish reeds, alternate leaves
• Also called Mexican bamboo
Leslie Kuhn
Partner in Crime: Giant
Knotweed (Fallopia sachalinensis)
• From Russia
• Less common in Michigan than JK
• A cross between Japanese and giant
(Fallopia X bohemica) generates
fertile seeds – has created a major
problem in UK
Giant knotweed
Fallopia X bohemica
Photos: Leslie Kuhn
Knotweed Leaf Differences
≤ 12”
≤ 6”
Above: michiganinvasives.org
Left: Bailey et al. (1996) Watsonia 21, 187
For learning to identify invasive species, see
very useful fact sheets & training modules at:
Plants Sometimes Confused with
Japanese Knotweed
Redbud (Cercis canadensis)
Pokeweed (Phytolacca americana)
Differences: has truly heart-shaped, soft
leaves (equally wide and long), and
branching woody stems (not reeds).
Differences: has brilliant solid pink-red stems
(not reeds with joints); leaves are narrower;
and has pink flowers and white berries.
Photo by B.S. Walters from michiganflora.net
Photo by Leslie Kuhn
What’s so Bad about Knotweed?
Fallopia japonica var. compacta
growing on lava in Japan
Japanese knotweed rhizomes & roots
Photo by John Cardina, The Ohio State University,
Bugwood.org, from
Photo from J. Bailey, Univ. of Leicester,
Roots grow up to 9’ deep and plants up to 15’ tall; can penetrate cement
< 1 gram of rhizome (size of a fingernail) can start a new plant
Stalk fragments can grow new roots and shoots from leaf nodes
There are no significant herbivores, insects or pathogens of Japanese
or giant knotweed in the western world
Knotweed Up-close and Friendly with Foundations
and Pavement at Apartments in East Lansing
Photos: Monica Day, Grand-Raisin Cluster of the Stewardship Network
• The spread is coming from roots or stalk fragments, not from
airborne seeds
• Can be very hard to control once it establishes under/within
An Ecological Nightmare:
Rivers on the Olympic Peninsula of Washington
One clump of JK on banks of the Hoh
River (UNESCO World Heritage Site)
within 5 years had spawned 18,585
canes downriver
Knotweed infestation and knotweed beaver
dam on the Big River, Olympic Peninsula
Excerpt from
Michigan Law on Invasive Knotweed
Prohibited Plant Species (Natural Resources and Environmental
Protection Act (Act 451 of 1994, as amended): Prohibited species
identified under this Act cannot be sold or grown in the state. Any of the
following plants, fragments [e.g, by cutting/mowing], seeds or a
hybrid or genetically engineered variant thereof are specifically
Photo of variegated Japanese knotweed cultivar
from Washington State University Clark County Extension
What is the Japanese Knotweed Situation in
Michigan and the Midwest? Ask misin.msu.edu
Homing in on Mid-Michigan Japanese Knotweed
Site #1, first
treated in
urban sites
not shown)
What patterns
do you see??
Mid-Michigan Stewardship Knotweed Treated Sites:
How to Prioritize? Depends on the Species
and Site Characteristics
• For invasive knotweed, rapid spread along rivers and trails and
roadsides is caused by cutting/mowing and stalk/rhizome breakage
Talman Rd. Bridge over the Looking Glass River in
Eagle, MI; photo by Nick Babcock, MSU Vets to Ag
• Outliers of a main population (satellites) are like burning embers!
• Highest priority: colonies or spread in/near high-quality habitats
• We aim to control all the observed sites in our area, one by one
Most Important Habitats to Protect from JK Invasion
Looking Glass River and Vermillion Creek
Sycamore Creek
Red Cedar River
landowner to:
inform them about
invasive species
describe why
treatment is
gain multi-year
permission to treat
plus liability waiver
Most landowners are
keen to treat, but find
specialty herbicides
In the field: It’s fun! A great workout and you
meet lots of interesting people and habitats!
Daily Summary Sheet for Each Treatment Site
Tracking Annual Permissions/Treatments/Monitoring
DEQ Aquatic Nuisance Treatment Permit: needed for any site with standing water at the time
of treatment: http://www.michigan.gov/deq/0,4561,7-135-3313_3681_3710---,00.html
Right-of-way (ROW) Permit: needed from road commission or municipality if site is within a
given distance of centerline of road (e.g.,33’ for a two-lane road in our area)
Pesticide Applicator Certification: needed if doing herbicide/pesticide application for your
job; see pested.msu.edu and MDARD Pesticide Applicator Certification
Our Experience with Herbicides for Foliar Spray
on Japanese Knotweed
Our wetland choice:
*Residual soil activity for
Our upland choice:
~18 mo. Do not spray
under redbud, locusts,
cedar, juniper, grape,
mimosa, mulberry, rose,
spruce, caragana, pinyon
pine. See Milestone link on
Helpful Resources page at
end of this document. Info
via Katie Grzesiak, IPN.
0.5% Imazapyr at Maguire Park: Full Japanese
knotweed control with no harm to neighboring trees
Progress in Japanese Knotweed Control
Japanese knotweed colony East Lake Drive in Haslett
Year 1, post-mowing
(mowing is no longer recommended)
Year 3
Wilted Japanese knotweed and Canada thistle
Three days after Milestone treatment
After 3 yrs Imazapyr and before Milestone treatment
2015 Control of Canada Thistle Succession by Using
Aminopyralid for a JK Site Previously Treated with Imazapyr
An Important Component! Collaborate with Parks, Road
Commissions, Utilities and Homeowners to Stop
Mowing/Cutting/Spreading Knotweed Along Roads and in
Yard Waste
Meeting with local parks
& city staff to brainstorm
on how to change
mowing practices to
reduce spread of
Japanese knotweed
How Long Does it Take to Win the Battle?
• Imazamox: 30-95% of invasive knotweed remained after 2 years
(problematic at more established sites; ceased using it)
• Imazapyr: 5-15% JK remaining after 2-3 years; important to use lower
0.5% concentration to not hurt nearby trees
• Aminopyralid: our first year of treatment, but it’s looking good, and
has worked well at MDNR treated sites
• Expect to keep monitoring for 4+ years after apparent control. Can
rebound in wet years.
• Stem injection or cutting-and-filling may be more effective but is
much more labor intensive; trade-off between # sites to treat and rate
of control
Stem methods contacts:
Carolyn Henne (NW MI
CWMA; Emily DuThinh,
Oakland County CISMA)
Stem injector kit; can be
connected to herbicide
reservoir (lower right) or
hose to herbicide
The Future: Japanese Knotweed Biocontrol
“In 2004, the psyllid [a type of louse], Aphalara itadori, was selected
for release in the UK and first releases made in the spring 2010 and
again in 2011 and 2012. In 2003-2005, release and control sites
were identified in OR and WA and data collected concerning
knotweed growth patterns. In 2012, similar release and control sites
were identified in MA, VT, and NH. In 2013, the TAG recommended
release of A. itadori in the US.”
From http://www.fs.fed.us/foresthealth/technology
Aphalara itadori, a natural
enemy and specialized feeder
on Japanese knotweed;
photo from The Independent
Community Flyer on
Identifying/Controlling Invasive Knotweed
New Community-wide Efforts to Control
Japanese Knotweed in Western Michigan
Maps c/o Randy Counterman, created by Kristin Schinske Adams
Kathy & Bill Hanley, The St. Joseph
Knotweed Eradication Group, Randy
Counterman (Native Landscapes), and
City of St. Joseph 2015
The Kalamazoo Bamboo Summit, 2015;
City of Kalamazoo and many stakeholders,
organized by Hannah Hudson
Some Helpful Resources
• See Japanese knotweed training module and fact sheet under “Learn” and best control
practices document under “How to” at: michiganinvasives.org
• This presentation will soon be posted at www.stewardshipnetwork.org/midmich under
• Maps and spreadsheets of known invasive knotweed locations under “Browse data” at
misin.msu.edu Upload your own data there individually or in bulk; see
• List of trees sensitive or not sensitive to aminopyralid/Milestone:
• Fascinating article on the history of Japanese knotweed and control efforts in the UK in
Harper's Magazine, May 2015: http://harpers.org/archive/2015/05/the-day-of-the-knotweed/
• MIPN Invasive Plant Symposium, Dec. 9-10, 2015 (Indianapolis, IN):
• Stewardship Network Conference Jan. 15-16, 2016 (East Lansing, MI) on the Science,
Practice, and Art of Restoring Native Ecosystems:
• Mid-Michigan Stewardship Initiative free community-oriented hands-on workshop on
Herbicide selection, safety, dilution, and application: Saturday, June 4, 2016; see
http://www.stewardshipnetwork.org for details in 2016 or contact [email protected]
Thanks to Lisa!
Any questions?

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