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Japanese Knotweed management in France

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• Lecturer : Julien Gaubert

• Author : Mireille Boyer

• Organisation :

CCEAU

Ecological Consultancy

Savoie – France

tel : 04-73-33-64-55

cceau.fr

- Regulation in France and local initiatives

- Improving comprehension to improve actions : diagnosis of invasion on rivers and development of

management strategies

- New methods of control: examples

Japanese Knotweed management in France

In order to preserve Natural Environments, their uses and the Wildlife,

it’s prohibited to introduce in Natural Environments intentionally or unintentionally : 1° any exotic and non-domestic Animal Species from the introduction area which is listed by ministerial order

2° any exotic and not normally grown Plant Species from the introduction area, which is listed by ministerial order

3° any animal or plant species designated by administrative authority.

Law - Environment Act (2005) : • Regulation in France & Local Initiatives

- no regulation on knotweed

- european regulation : project in progress

List (2007) :

Mammifères : Wallaby de Benett / Chien viverrin / Vison d'Amérique Raton laveur / Cerf sika / Toutes espèces de sciuridés sauf la marmotte et l’écureuil roux Castor canadien / Rat musqué / Ragondin /Rat surmulot / Lapin américain Oiseaux : Erismature rousse ; Ibis sacré; Bernache du Canada ; Ouette d'Egypte ; Perruche à collier. Reptiles : Toutes les espèces appartenant aux genres suivants : Chrysemys spp. ; Pseudemys spp. ; Trachemys spp. ; Graptemys spp. ; Clemmys spp. Amphibiens : Xénope lisse ; Grenouille Taureau ; Grenouille verte de Bedriaga ; Grenouille verte des Balkans

List (2010) :

Plants : Primrose willow - Ludwigia grandiflora et Ludwigia peploides.

Japanese Knotweed management in France

Knotweed production in France as biomass

Official Gazette of plants authorised for cropping (mars

2009)

• Regulation in France & Local Initiatives

- 2 varieties can be cultivated in EU : Igniscum et Candy

Japanese Knotweed management in France

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Knotweed production in France as biomass

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• Regulation in France & Local Initiatives

- 2 varieties can be cultivated in EU : Igniscum et Candy

- 2 ha cultivated in 2009 in a farm turned into energy production in Weinbourg (Alsace)

Japanese Knotweed management in France

• Towards the integration of preventive measures in building sites

- e.g. : in Savoy with support of County technical services

Project : extraction of infested gravel bar to restore the capacity & strengthen of dikes on river Isère.

problem:

non-infested dike

infested bar Experimentation of control methods :

compacting + crushing - covering

Area : 20 000 m²

Height : 4 to 5 m

Volume of the backfill : 74 000 m3

Increase of the project’s cost : + 10 %

• Regulation in France and Local Initiatives

- many local initiatives

Japanese Knotweed management in France

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3 4

1 – ASSESS THE INVASIVE STAGES

effective actions with small impacts

non-effective actions with important impacts

2 – ACTING ON THE PROPAGULES TRANSITS AND ON A COHERENT WATER SYSTEM

priority goal with Japanese Knotweed : to stop or to slow the spread of the plant

• Improving comprehension to improve actions :

- mapping and diagnosis

- management objectives

Japanese Knotweed management in France

m²/ 500 m

u/ 500 m

118 sections (invasive stages) 21 rivers 59 km of waterways

infested area

number of clumps

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• Improving comprehension to improve actions

- évaluer les stades invasifs

Japanese Knotweed management in France

20 m² / 500 m of river

8 clumps / 500 m of river

removal or confinement of every clumps

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• Improving comprehension to improve actions

- assess the invasive stages

STAGE 1

Japanese Knotweed management in France

500 m²/500m of river

15 clumps / 500 m of river

STAGE 4

no control (except in case of major threat on wildlife or uses)

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• Improving comprehension to improve actions

- évaluer les stades invasifs

Japanese Knotweed management in France

mechanical control (crushing covering)

shoots removal

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• Improving comprehension to improve actions

- example of management strategy applied to the Watershed of Lake of Bourget (Savoie)

Japanese Knotweed management in France

Early manual shoots removal (coming from snatched rhizomes or cuttings)

• Many non-chemical and operative methods

- many methods already exists

- many more have to be developed

• Change habits

- we have too

we have to !

Mechanical removal of Knotweed from soil or alluvium

Confine Knotweed

it works !

Cutting knotweed without spreading

etc.

Moving infested materials without spreading

etc.

it is expensive

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Japanese Knotweed management in France

1 y.o. 4 y.o.

• Many non-chemical and operative methods

- Manual shoot removal (coming from snatched rhizomes or cutting)

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Japanese Knotweed management in France

Linéaire prospecté Nombre de plantules repérées et éliminées

Temps passé en h

2012 2013

84 km de rivières 388 280 500 45 km de littoral

lacustre 267 > 351* 140

* données incomplètes

• Many non-chemical and operative methods

- Manual shoot removal (coming from snatched rhizomes or cutting)

- example in Savoie

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Japanese Knotweed management in France

location of the experimentation sites (2005-2013)

• Many non-chemical and operative methods

- the crushing-covering

Japanese Knotweed management in France

-I- Digging and

levelling Efficiency and

spreading control

-II- Crushing

Effectiveness control

-III- Covering

Ballast control & set up of samples

of rhizomes

-VI- Resumption Removal of

remaining plants

-V- Foil removal Effectiveness control of the

rooting process

Asiatic knotweed management in France

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excavation from a rocky area

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Worksite operations

some tools for crushing storage under opaque

foil for rotting

• Many non-chemical and operative methods

- the crushing-covering

dismantled rocky embankment

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Japanese Knotweed management in France

• Coverage time

– Rotting time vary from site to site depending on humidity : 48 to 70 weeks.

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• Many non-chemical and operative methods

- the crushing-covering

Japanese Knotweed management in France

le Buëch, a braided river

stage 1 -> quick and complete removal of the plant

150 clumps 25 km of river infested

total cost (2009 - 2013) (diagnosis, test and works) : 280 000 €TTC

processed volume : 6 000 m3

• Many non-chemical and operative methods

- application example