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ai:LABThe Knotweed PaperOptimising physiochemical control of invasive Japanese knotweed

23.07.2018version_1

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ai:LAB invasives research | © 2018

PartnersSwansea University Department of BiosciencesComplete Weed Control

ContactAdvanced Invasives Limited

Dr Dan JonesManaging Director

e: www.advancedinvasives.comw: [email protected]: (+44) 7967 408844

Institute of Life Science 2Swansea UniversitySingleton ParkSwanseaSA2 8PP

Registered in England and Wales Number: 10080998

DocumentCreation: Dan ClugstonReview: Dan JonesRelease: Dan Jones

Issue: version 1 Date: 23.07.2018

ai:LAB, August 2012: Uncontrolled plant growth creating a Japanese knotweed ‘forest’ in Taffs Well.


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About Advanced InvasivesAdvanced Invasives was founded in 2016 by Dr Dan Jones (PhD, GCIEEM) and Dr Gareth Bruce (PhD), bringing together over twenty years of experience in applied plant ecology.

We are a South Wales based consultancy that solves complex invasive plant species problems, with a specialist focus on Japanese knotweed.

We want Advanced Invasives to set a new standard of invasive species management; scientific, applied and bridging the gap between research and public understanding of invasive species management.

About ai:LABai:LAB is Advanced Invasives continuous research and field-trial project, undertaken in partnership with Swansea University’s Department of Biosciences.

In 2018 we completed the world’s largest field-trial on Japanese knotweed. A seven year research project involving three years of experiments, and testing nineteen of the main physical and chemical methods of controlling Japanese knotweed in the UK.

Our research is unique in terms of scale, duration, and scientific rigour. We’re using it to replace outdated industry guidance based on short-term experiments and anecdotal information.


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Modern invasives species managementModern invasives species management needs to consider much more than mere treatment - applying herbicide control or undertaking physical remediation is only the final stage of managing invasive plants and the problems they cause.

Before use in any invasives treatment, new herbicide formulations and methods of application need to be tested. New products need to be supported by an independent evidence-base, and public facing guidance needs to be scientifically accurate.

We understand that large organisations and national landowners have often inherited an invasives problem through no fault of their own. Nationwide green estates, and land assets in urban spaces are prone to invasion and re-colonisation by invasive plants. Reactive treatment is not enough. Intelligent and long-term invasives strategy is needed.

At the same time, public awareness of invasives is increasing. Homeowners need clear information and reassurance, and large landowners are under pressure to give accurate guidance, prioritise treatments, and also reduce future liability from invasives problems.

Our role is to help our clients tackle any of the problems caused by invasive plants that may be affecting their organisation, and in turn impacting upon their clients and customers.


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Our valuesWe founded Advanced Invasives to apply our scientific understanding of invasive plant ecology to real world problems.

Unlike most other companies in the industry we are non-partisan to any one species or control method. Instead, we are evidence-led and consider invasive plant problems from the ground up across the whole treatment lifecycle.

What we doWe help people and organisations understand invasive plant problems and how best to resolve them.

Our projects cover six main areas:

• Field research and product testing• Risk mapping and GIS• Advisory and public engagement• Invasives strategy• Site assessment• Physical & chemical control

ai:LAB, May 2015: The knotweed forest is brought under control. Note the dense stand of the control plot (foreground).

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The Japanese Knotweed Paper

Optimising physiochemical control of invasive Japanese knotweed

Date: April 2018Journal: published in Biological Invasions

Authors: Daniel Jones, Gareth Bruce, Mike S. Fowler, Rhyan Law Cooper, Ian Graham, Alan Abel, Alayne Street-Perrott, and Daniel Eastwood

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Context From 2011-2018 Dr Dan Jones, in partnership with Swansea University and Complete Weed Control, undertook the world’s largest ever field-trial and peer reviewed research project on Japanese knotweed.

Some key facts:

• 3 geographically similar field-sites across the UK• 12 acre main site in Taffs Well, Wales• 19 active treatments tested• 58 treatment and control plots• 225 metre squared plot areas• 348 randomised sampling plots• £1.2m commercial costing

The scientific paper; Optimising Physiochemical Japanese Knotweed Control in the UK, summarises the results of the field-trial, and is published entirely open access in the American journal; Biological Invasions, April 2018.

The scope of the research is unique.

In terms of scale, duration and scientific rigour, the work surpasses outdated industry guidance based on short-term experiments and mostly anecdotal data.

Our key findings:

• None of the treatments tested achieved eradication• Glyphosate-based herbicides are the most effective

treatments for controlling Japanese knotweed• Non-glyphosate-based herbicides are ineffective• The physical control methods tested are ineffective

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Site SelectionThree separate, but geographically and geologically similar sites of large-scale knotweed infestation were selected for the field-trials.

The main twelve acre site was Taffs Well, in Cardiff. Two smaller supporting research sites were; Lower Swansea Valley Woods, and Swansea Vale Nature Reserve, both in Swansea.

Treatments were divided into:

• Taffs Well herbicide protocols, and integrated cutting treatment

• Lower Swansea Valley Woods rhizome tillage with herbicide application

• Swansea Vale Nature Reserve aboveground covering treatment with hand-pulling


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Aerial photograph of the main field trial site at Taffs Well showing arrangement of the 54 field trial plots and

one control plot (red). Four experimental blocks were created at the site between May 2012 and May 2013.

Key

Block 1

Block 2

Block 3

Block 4

CONTROL

Scale15m

Aerial photograph of the main field trial site at Taffs Well showing arrangement of the 54 field trial plots and

one control plot (red). Four experimental blocks were created at the site between May 2012 and May 2013.

Key

Block 1

Block 2

Block 3

Block 4

CONTROL

Scale15m

Aerial of treatment plots: Block 1 (yellow), Block 2 (blue), Block 3 (green), Block 4 (orange), and Control (red).

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N

Taffs Well research site

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a8Early springPicloram (Tordon 22K®) foliar and soil sprayAutumnGlyphosate (Glyfos Proactive®) foliar spray

a9Spring (tank mix)Aminopyralid & fluroxypyr (product mix) (Synero®) foliar sprayGlyphosate (Glyfos Proactive®) foliar sprayAutumn (single product)Glyphosate (Glyfos Proactive®) foliar spray

a10SpringAminopyralid & fluroxypyr (product mix) (Synero®) foliar sprayAutumn (single product)Glyphosate (Glyfos Proactive®) foliar spray

a11Spring (tank mix)Flazasulfuron (Chikara®) foliar sprayGlyphosate (Glyfos Proactive®) foliar sprayAutumn (single product)Glyphosate (Glyfos Proactive®) foliar spray

a12Early springFlazasulfuron (Chikara®) soil sprayAutumnGlyphosate (Glyfos Proactive®) foliar spray

a13Spring (tank mix)Flumioxazin (Digital®) foliar sprayGlyphosate (Glyfos Proactive®) foliar sprayAutumn (single product)Glyphosate (Glyfos Proactive®) foliar spray

Soil and foliar spraysa1 Autumn Hi rateGlyphosate (Glyfos Proactive®) foliar spray

a2Autumn LO rateGlyphosate (Glyfos Proactive®) foliar spray

a3SummerGlyphosate (Glyfos Proactive®) foliar sprayAutumnGlyphosate (Glyfos Proactive®) foliar spray

a4Spring2,4-D (Depitox®) foliar sprayAutumnGlyphosate (Glyfos Proactive®) foliar spray

a5SummerGlyphosate (Glyfos Proactive®) foliar sprayAutumn (tank mix)2,4-D (Depitox®) foliar sprayGlyphosate (Glyfos Proactive®) foliar spray

a6Spring2,4-D (Depitox®) foliar sprayAutumn (tank mix)2,4-D (Depitox®) foliar sprayGlyphosate (Glyfos Proactive®) foliar spray

a7Spring (tank mix)2,4-D (Depitox®) foliar sprayGlyphosate (Glyfos Proactive®) foliar sprayAutumn (tank mix)2,4-D (Depitox®) foliar spray Glyphosate (Glyfos Proactive®) foliar spray

Experiments19 commercially active Japanese knotweed treatments were tested over three years, using triplicate 225 m2 plots (with the exception of covering), with one control plot at each field-trial site.

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Integratedd1SummerCutting of above-ground knotweed growthAutumnGlyphosate (Glyfos Proactive®) foliar spray

d2SpringDigging and turning of knotweed rhizomeAutumnGlyphosate (Glyfos Proactive®) foliar spray

d3SpringDigging and turning of knotweed rhizomePicloram (Tordon 22K®) foliar and soil sprayAutumnGlyphosate (Glyfos Proactive®) foliar spray

d4All yearCover with Viqueen® 300 μm (1200 gauge) HDPE geomembraneAll yearHand pull emergent knotweed

Cut and fillb1AutumnGlyphosate (Glyfos Proactive®) cut & fill

Stem injectionc1AutumnGlyphosate (Glyfos Proactive®) stem injection

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Sampling strategy: Six randomised 4m² monitoring patches taken within each 225m² testing plot.

Treatment typesFour types of Japanese knotweed treatments were tested:

• Soil and foliar spray (green)• Cut and fill (blue)• Stem injection (red)• Integrated physiochemical (yellow)

Taffs Well, plots by treatment: Experiments undertaken in triplicate, with control plot (in grey).

1Qa8

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ctrl

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Taffs Well, plots by phase: Block 1 (yellow), Block 2 (blue), Block 3 (green), Block 4 (orange), and Control (grey).

Experiment blocksTreatments were divided in four blocks of semi-randomised experiments, with a single, constant control plot for reference.

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Block 2, Plot J

Treatmentgroup a4

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Experiment TimingExperiment timing, by block, was informed by growing season constraints, and legal restrictions such as use near water:

• Block 1 Pre-treatment assessment: September 2012 Treatment begins: March 2013 Treatment evaluation: September 2014

• Blocks 2 Pre-treatment assessment: April 2013 Treatment begins: May 2013 Treatment evaluation: May 2015



An intitial year of pre-treatment assessment took place, followed by treatment evaluation at two years post treatment, making the experiments three years in total duration. End to end the research project covered seven years, starting in 2011 and concluding in 2018.

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Treatment EvaluationAnnual plot assessment was undertaken in spring or autumn before control treatment application using six randomly assigned 4 m2 monitoring patches within each field trial plot.

Data captured included:

• Aboveground stem density• Basal percentage cover• Light utilisation efficiency

Whole plant maximum light utilisation efficiency (Fv/Fm) of photosystem II (PSII) was measured using a chlorophyll fluorescence system. Mean whole plant Fv/Fm was derived from leaf measurements taken at 25, 50 and 75% of total plant height (to reflect leaf age), with six representative plants measured within each treatment and control plot.

The above three responses were assessed to provide a complete picture of the response of knotweed to treatments, accounting for:

• Absolute basal cover reduction• Deformed regrowth• Potential photosynthetic capacity• Whole plant photosynthetic efficiency and

physiological state.

Basal cover measurements were made at ground level and recorded deformed regrowth, providing a good indicator of recovery from physiochemical treatments, particularly herbicides.

ai:LAB, October 2014: Dieback of the surface knotweed plant in Autumn, as plant energy is drawn down into the rhizome.

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Key Finding 1 EFFECTIVENESS OF GLYPHOSATE ALONE

What the paper says “Greatest control of aboveground F. japonica growth, defined by reduced basal cover and stem density, was obtained using glyphosate alone, where application timing was coupled to photosynthate flow to the rhizome.”

What the paper meansOf the 19 treatments tested 3 were found to be significantly more effective at controlling Japanese knotweed than all of the others. These were the treatments based on the application glyphosate alone, applied at the right time of year - when knotweed energy is being drawn from the aboveground plant into the rhizome.

In order of most effective first, these are:

• Twice yearly foliar spray of glyphosate-based herbicide• Annual stem injection of glyphosate-based herbicide• Annual foliar spray of glyphosate-based herbicide

For all practical purposes twice yearly foliar spray, and annual stem injection performed equally well.

Annual foliar spray was not as effective as either twice yearly foliar spray, or annual stem injection. However it is still a very effective treatment and in practice can be a more pragmatic choice for strategic knotweed treatment.

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Key Finding 2INEFFICIENCY OF STEM INJECTION IN TERMS OF GLYPHOSATE DOSE

What the paper says“It is notable that stem injection required 15.07 times more glyphosate per unit area than either [twice yearly half label rate, or annual full label rate] spray treatment and was more labour intensive to apply.”

What the paper meansStem injection is effective at controlling knotweed. However it is time consuming and uses an extremely high dose of glyphosate compared to foliar spraying.

In most instances stem injection should be used as a secondary option to foliar spraying - perhaps when weather or geographic conditions prevent spraying.

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Key Finding 3MANAGEMENT OF JAPANESE KNOTWEED USING HERBICIDE TREATMENTS IS ABOUT CORRECT TIMING, NOT INCREASING DOSE EXCESSIVELY

What the paper says “Upon foliar application, glyphosate penetrates rapidly through the plant cuticle prior to slow symplastic uptake. Glyphosate then moves to metabolically active sink tissues with high expression of EPSPS, i.e. F. japonica [Japanese knotweed] rhizome meristems (active shoot clump and rhizome buds), while aboveground tissues display limited herbicide injury. Although there is a linear relationship between glyphosate dose and tissue concentration (Feng et al. 2003), the distribution across leaf, stem and root tissues in F. japonica is independent of dose and is determined by sink strength (Buschmann 1997). This contrasts with smaller, annual dicotyledonous plants that respond in a dose-dependent manner at the whole plant level (Gomes et al. 2014). Mature F. japonica leaves provide a strong source of glyphosate and its relatively slow mode of action means that translocation to active rhizome sink tissues can be achieved (Cerdeira and Duke 2006).”

What the paper meansEffective herbicide treatment of Japanese knotweed is about applying herbicide at the right time of year and having a ‘healthy’ plant to effectively transport glyphosate into the rhizome.

Beyond the threshold dose of glyphosate needed for effective treatment, managing Japanese knotweed using glyphosate-based herbicides (foliar spraying or stem injection) is about getting good coverage of the whole plant with herbicide.

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Key Finding 4INEFFECTIVENESS OF NON-GLYPHOSATE HERBICIDES

What the paper says“The application of synthetic auxins 2,4-D amine, picloram, aminopyralid and fluroxypyr (TGs a4 to 10, d3), ALS inhibitor flazasulfuron (TGs a11 and 12), and PPO inhibitor flumioxazine (TG a13) did not significantly reduce long-term basal cover or stem density compared with two foliar glyphosate treatments (TG a3).”

What the paper meansNon-glyphosate-based herbicide treatments for Japanese knotweed are not as effective as glyphosate-based treatments.

Synthetic auxins, ALS inhibitors and PPO inhibitors should not be used to control Japanese knotweed, unless there is a compelling reason to do so.

Note: Picloram has since been deregulated and lost it’s license for legal use in the EU. It is no longer available as a treatment option for Japanese knotweed in the UK.

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Key Finding 5INEFFECTIVENESS OF THE PHYSICAL AND INTEGRATED PHYSIOCHEMICAL TREATMENTS TESTED

What the paper says “Geomembrane covering (TG d4) was the least effective control treatment in reducing the response parameters (Online Resource 6). Integrating physical control methods with glyphosate treatments did not improve F. japonica control compared with glyphosate alone, i.e., summer cutting and autumn glyphosate application (TG d1), spring excavation and autumn glyphosate (TG d2) and autumn cut and fill (TG b1).”

What the paper means Covering knotweed with an aboveground sheet or tarpaulin is not an effective method of control (note - this should not be confused with full geomembrane encapsulation).

Physiochemical treatments that com––bine glyphosate-based herbicide application with either stem cutting (such as cut and fill) or rhizome tillage do not improve Japanese knotweed control, compared to applying herbicide alone.

Summer cutting before herbicide application, rhizome tillage before herbicide application and cut and fill interfere with the effectiveness of the initial herbicide treatment and therefore should be discontinued.

Physical methods alone, such as aboveground covering, hand-pulling of shoots, hand-digging, and also mowing, strimming, and cutting are ineffective. These methods are also time consuming and likely to increase the risk of inadvertent knotweed spread - they should be discontinued.

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Key Finding 6MANAGEMENT OF JAPANESE KNOTWEED USING HERBICIDE TREATMENTS IS A QUESTION OF CONTROL, NOT ERADICATION

What the paper says “Though no control treatment delivered complete eradication of F. japonica within 3 years of the first treatment application, glyphosate applied at an appropriate dose, phenological stage and level of coverage (using foliar spray and stem injection application) was found to be the most effective control treatment.”

What the paper meansOf the 19 treatments tested, none achieved complete kill of the knotweed plant/rhizome system.

Management using stem injection and foliar spray (the most effective of the treatments tested) is therefore more a question of control, not eradication.

However this does not mean that knotweed cannot be successfully managed. There are well established processes in the industry for issuing management plans with insurance backed guarantees to cover multi-year courses of herbicide treatment.

NoteThe paper does not consider mechanical excavation with off-site disposal (so called ‘dig and dump’), or full geomembrane encapsulation - treatments that are widely used to remediate Japanese knotweed on development sites, and at times on residential premises. These treatments are often advertised as ‘eradicating Japanese knotweed’. We suggest this is an unhelpful use of the word eradication. ‘Achieving effective control’ is a more accurate phrase.

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Key Finding 7FUTURE DEREGULATION OF GLYPHOSATE RAISES IMPORTANT QUESTIONS FOR JAPANESE KNOTWEED CONTROL

What the paper says “While we recommend glyphosate use, it is acknowledged that there is a need to identify further herbicides or control approaches to reduce the potential risk of invasive hybrid knotweed populations developing resistance to the single effective herbicide. Rhizome-forming invasive species incur long-term ecological and socioeconomic costs, while few effective management tools are available, as shown by this study. Crucially, this experiment warns of further deregulation of herbicides, such as glyphosate and picloram, without equivalent replacement will lead to the application of greater quantities of ineffective herbicide products and reduce the viability and sustainability of F. japonica control.”

What the paper meansIn the UK, Japanese knotweed reproduces almost exclusively clonally, so is very unlikely to develop resistance to herbicides. Bohemian knotweed is a hybrid species so there is the possibility of it developing resistance to glyphosate.

The loss of glyphosate as an available method of Japanese knotweed control would likely lead to the use of alternative herbicides that are much less effective. These alternative herbicides would also likely be applied in greater quantities, and with higher dosages of active ingredients. The environmental impact of alternative herbicides to glyphosate should consider the full ecotoxicological profile over the treatment life-cycle needed to achieve like-for-like effective control of Japanese knotweed.


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The 4-Stage ModelNow updated with the results of the paper, The 4-Stage Model links herbicide selection and application with the seasonal changes in the surface-to-rhizome energy flows of the knotweed plant.

The main seasonal changes in knotweed physiology across the year are:

Plant growth cycle:• February-April: pre-emergence• May-June: mid-growth• June-July: maximum growth• August-November: flowering

Rhizome energy flows:• February-April: strong source• May-June: transitioning from source• June-July: transitioning to sink• August-November: strong sink

As the bridge between herbicide chemistry and knotweed physiology The 4-Stage Model gives us an intelligent and precise ability to fine-tune the chemical control of Japanese knotweed.

Seasonal targeting of treatment gives more effective outcomes using lower doses of herbicide across the whole treatment lifecycle. This means more affordable treatment that is more environmentally sound than traditional, blanket application of herbicides.


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STAGE 1

February-April

Pre emergence

iRhizome system initially dormant. Budding of new growth as air and soil temperatures rise in early spring.

iiRhizome reserves mobilised, new shoots budding.

iiiRhizome is strong SOURCE

RecommendationDo not use

RecommendationUse

RecommendationUseNo longer available

ivTheory: persistent (residual) herbicides disrupt above and below ground growth from early in the growing season e.g. Picloram.

STAGE 2

May-June

Spring - mid growth

iRhizome system active, supplying resources for growth of stems and leaves, and supporting development of knotweed canopy.

iiFlow of rhizome resources to developing shoots and leaves, resources captured by new growth are incorporated into aboveground tissues.

iiiRhizome transitioning

from SOURCE

ivTheory: apply herbicides that disrupt metabolism and growth, while knotweed growth is maximal e.g. synthetic auxinsPPO inhibitors, ALS inhibitors.

STAGE 3

June-July

Summer - maximum growth

iRhizome growth to expand storage capacity. Maximum height of stems is reached, prior to further increase in leaf area prior to flowering.

iiOnce source-sink transition point is reached, flow of resources from aboveground growth to rhizome increases.

iiiRhizome transitioning

to SINK

STAGE 4

August-November

Autumn - flowering

iRhizome system active sink for resources captured by aboveground tissues in the growing season, flowering and senescence.

iiFlow of resources from aboveground tissues to rhizome.

iiiRhizome is strong SINK

ivTheory: apply glyphosate-based herbicide that is transported strongly from aboveground tissues into the r h izome system e.g. glyphosate-based herbicides.

ivTheory: apply glyphosate-based herbicide that is transported strongly from aboveground tissues into the r h izome system e.g. glyphosate-based herbicides.

The 4-Stage Model: Advanced Invasives’ seasonal Japanese knotweed treatment model.

ai:lab€¦ · 3h b1 1g a11 1f a8 1e a12 1d a9 1h a10 1k a9 1l a13 1j a11 1m a8 1l a12 1p a9 1o a13...

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