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Japanese Knotweed Ecology and Evidence.
Dr Dan Jones
Japanese knotweedFallopia japonica var. japonica
Dwarf knotweedF. japonica var. compacta
Giant knotweed F. sachalinensis
Bohemian knotweed F. × bohemica
Japanese knotweed s.l.‘in the broad sense’
Japanese knotweedFallopia japonica var. japonica
Giant knotweed F. sachalinensis
Bohemian knotweed F. × bohemica
ContractorCase studiesCustomer feedbackINNSA 2018
Experts?
AcademicChild & Wade 2000
Swansea / CWC 2018Leeds / AECOM 2018
Government & IndustryEnv. Agency 2006
RICS 2012PCA 2014
InformationAnecdotal v Systematic
Types of evidence
DurationSingle-year v Multi-year
ScaleResidential v Strategic
Anecdotaldata
Limited guidance
Industryfolklore
+ =
ai:LABSwansea University
ResearchPhD field-trial
Advanced Invasives
Consulting
The Knotweed
Paper
Evidence-base
2016-onwards2011-2016 2018
We solve invasive species problems
StrategyResearch & TestingPublic GuidanceRisk MappingSite SurveyExpert Witness
Secondary SitesLower Swansea Valley Woods: rhizome tillage w. herbicideSwansea Vale Nature Reserve: covering with hand-pulling
Main SiteTaffs Well: herbicide only, and herbicide with cutting
58treatment plots in total
225metre squared plot areas
348randomised sampling plots
4treatment types
12acre main field site in Taffs Well
19experiments in triplicate, with controls
Invasives require parsimony
Key ideas
Right herbicide, right timeNeed to consider seasonal energy flows between aboveground foliage and belowground rhizome
Foliage as the pump, rhizome as the batteryTreatments that damage knotweed aboveground growth jeopardise treatment efficacy
Integrated physical and chemical treatments have poor outcomesWe need to use herbicides!
Control, not eradicationNo treatment achieved total kill
The 4-Stage ModelTM
What works?
Of the 19 treatments tested only 3 were statistically effective:● Biannual foliar spray (glyphosate)● Stem injection (glyphosate)● Annual foliar spray (glyphosate)
Stem injection is dose inefficient (at present!)Requires 15.84 x dose of glyphosate compared to foliar spraying
More is not betterBeyond a threshold dose, higher dose +/- more glyphosate treatments do not improve outcomes
We need glyphosate!
Timing
Seasonal window
Herbicide
Glyphosate
Dose
Threshold
Coverage
Translocation
Thank you
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