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Optimising PhysiochemicalJapanese Knotweed Control
Dr Daniel Jones
Presentation Overview• Brief introduction to the target taxa• Knotweed control – current best
practice• Field trials – design & progress• Results & analysis• Further work
Japanese Knotweed1. Ecological impacts:• Reduced habitat availability and
quality• Disruption of terrestrial and
freshwater food webs (Gerber et al. 2008)
2. Socioeconomic impacts: • Built environment (e.g. development
sites)• Recreation and landscape (e.g.
angling)3. Control costs:• £165.6 million PA for UK• £8.8 million PA for Wales (Williams et
al. 2010)• In excess of £1.5 billion for complete
eradication in UK (Shaw et al. 2009)
Japanese knotweed (Fallopia japonica var. japonica) Welsh National Herbarium
specimen
Knotweed – The Main CulpritsJapanese knotweed stand (F. japonica var. japonica), Cardiff
(UK)
Dwarf knotweed stand (F. japonica var. compacta), Merthyr Tydfil
(UK)Bohemian knotweed stand
(F. x bohemica), Cardiff (UK)
Giant knotweed stand (F. sachalinensis), Cardiff (UK)
UK Distribution of Japanese Knotweed s.l. Taxa
Bohemian knotweed (F. x bohemica)
Giant knotweed (F. sachalinensis)
Japanese knotweed (F. japonica var. japonica and
compacta)
Available from: http://data.nbn.org.uk/
Physical ControlCurrent best practice
Summary of physical control methods (EA 2006)
Chemical ControlCurrent best practice
Summary of chemical control methods (EA 2006)
Despite proven ecological and socioeconomic impacts, we still do not know enough to make
good, evidence-based decisions
Field Trial RationaleIdentified need for large-scale and long-term field experiment (>3 years duration) to:• Test control efficacy of widely applied and
novel control methods• Investigate control method costs and
environmental impacts• Site restoration following knotweed control
How Are We Testing?• Largest knotweed control experiment ever
undertaken – sixty-five 225 m2 field trial plots• Greatest number of control treatments ever
trialled for control of a single invasive species – 24 currently under investigation
• One of the longest running invasive species field trials, worldwide (Kettenring & Adams 2011)
Field Trial Site Locations
Field Trial Site LocationsSite 1: Lower Swansea Valley Woods (LS),
Swansea
Field Trial Site LocationsAerial view of site 2013
Field Trial Site LocationsSite 2: Swansea Vale Nature Reserve (SV),
Swansea
Field Trial Site LocationsAerial view of site 2013
Field Trial Site LocationsSite 3: Taffs Well (TW), nr. Cardiff
Field Trial Site LocationsAerial view of site 2013
‘By their very nature chemical controls are self-defeating, for they have been devised and applied without taking into account the complex biological systems against which they have been blindly hurled.’
Rachel Carson (1962)
Knotweed Physiology
Rhizome PhysiologyRhizome:• Rhizomes (roots) are robust &
extensive and are functionally similar• Root system >65 % total biomass• Most found in the top 1m of soil,
though roots reported deeper than 4.5 m (Jones 2015)
• Rhizome can extend ≤20 m from the main stand and grow ≤3 m per year (Beerling et al. 1994)
Dispersal: • Rhizome fragments (diaspores)• Direct rhizome expansion (Bailey et
al. 2009)
Shoots emerging 10 m away from main stand
(Briton Ferry, Wales, UK)
Control Implications• Physical methods ineffective due to significant
energetic reserves – also encourage spread• Rhizome exhibits strong seasonal changes in
herbicide uptake • Deep rhizome is distant from the point of
herbicide application• Is there a herbicide dose-response
relationship?• Most herbicides formulated and tested on
annual plant species (e.g. synthetic auxins)
Source-Sink RelationsKnotweed source-sink relations and implications for herbicide application
Knotweed regrowth following glyphosate treatment (Cardiff: A = 14/07/09; B = 24/07/11)
HerbicidesALS inhibitor:• Flazasulfuron (Chikara®) PPO inhibitor: • Flumioxazine (Digital®)• Oxadiazon (Ronstar Liquid®) AAA inhibitor: • Glyphosate (Glyfos Proactive®) Synthetic auxin: • 2,4-D amine (Depitox®)• Aminopyralid & triclopyr (Icade®)• Aminopyralid & fluroxypyr (Synero®)• Picloram (Tordon 22K®)
Application Methods• Spraying• Stem injection• Cut & fill• Turning before herbicide
application• Cutting before herbicide
application
Knotweed excavation at Lower Swansea Valley Woods
Treatment Schedule
Treatment SchedulePre-emergent treatment window
Treatment ScheduleLate spring / summer treatment window
Treatment ScheduleLate summer / autumn treatment window
Testing Control Response• 225 m2 treatment area• 6× 4 m2 monitoring
patches, assigned at random
• Treatment plots were treated in their entirety
• Control plots received no treatment
Scale drawing of treatment plot
ParametersMonitoring patch data capture:• Aboveground knotweed growth parameters• Plant stress measures • Vascular plant species diversity • Soil parameters
Glyfos ProActive® 689 DAT10.00 L ha-1 (3.60 kg AE ha-1) glyphosate
Tordon 22K® & Glyfos ProActive® 797 DAT11.20 L ha-1 (2.69 kg AE ha-1) picloram &10.00 L ha-1 (3.60 kg AE ha-1) glyphosate
ObservationsLower Swansea Valley Woods
October 2014
Covering treatment 888 DAT
ObservationsSwansea Vale Nature Reserve
October 2014
ObservationsTaffs Well
October 2014
Spray alone (left) and cut with spray (right) Glyfos ProActive® 404 DAT
10.00 L ha-1 (3.60 kg AE ha-1) glyphosate
ObservationsTaffs Well
October 2014
Cut & fill (left) and stem injection (right) Glyfos ProActive® 407 and 389 DAT
244.44 & 180.89 L ha-1 (80.00 & 65.12 kg AE ha-1) glyphosate
Synero® & Glyfos ProActive® 508 DATSynero® 2 L ha-1 (0.06 kg AE ha-1 aminopyralid &
0.20 kg AE ha-1 fluroxypyr) & 10.00 L ha-1 (4.32 kg AE ha-1) glyphosate
Tordon 22K® & Glyfos ProActive® 568 DAT11.20 L ha-1 (2.69 kg AE ha-1) picloram &10.00 L ha-1 (3.60 kg AE ha-1) glyphosate
ObservationsTaffs Well
October 2014
Chikara® & Glyfos ProActive® 506 DAT25 % w/w (0.15 kg AE ha-1) flazasulfuron &
6.00 L ha-1 (4.32 kg AE ha-1) glyphosate
Chikara® & Glyfos ProActive® 568 DAT25 % w/w (0.15 kg AE ha-1) flazasulfuron &10.00 L ha-1 (3.60 kg AE ha-1) glyphosate
ObservationsTaffs Well
October 2014
Digital® & Glyfos ProActive® 508 DAT0.10 L ha-1 (0.03 kg AE ha-1) flumioxazine &
6.00 L ha-1 (4.32 kg AE ha-1) glyphosate
Ronstar Liquid® 223 DAT8.00 L ha-1 (2.00 kg AE ha-1) oxadiazon
ObservationsTaffs Well
October 2014
Results & Analysis• Data for 1st 3 years of field trials now in publication, forming
the basis of best practice guidance for:- Royal Institute for Chartered Surveyors (RICS) and - Property Care Association (PCA)• Full economic evaluation and Life Cycle Assessment (i.e. CO2
emissions) of all control methods• Community analysis of vascular plant data• Soil analysis (physical, chemical & biological)
Further Work• Treatment of Himalayan balsam underway• Expansion of field trial programme to include:- Additional herbicides- New application technologies- Test efficacy of widely applied and novel physical
eradication methods
Informing Industry• Experimental data (supporting evidence) are
essential for informing Integrated Plant Management (IPM) control strategies
• Such data reduce operational costs and environmental impacts, increasing sustainability
• In the face of increasing pesticide deregulation, studies such as these form an essential source of evidence for regulators
• Consolidation in Ag industry will make it more important for industry to find solutions in concert with universities
Project Partners:
Part-funded by the European Social Fund (ESF) through the Welsh Government with Swansea University and Complete Weed Control Ltd.
Project Acknowledgements: