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