Title: Dr. Leonie Richardson
1Presentation Title
The Great Japanese Knotweed Debate
- Dr. Leonie Richardson
- Science Shops Wales
2Introductory History
- Native to East Asia
- Introduced to UK mid 19th Century as an
ornamental plant and for fodder - International Union for Conservation of Nature
Top 100 list of invasive species - Distinct British female clone, Fallopia japonica
var. Japonica
3Identification and Biology
- Young shoots appear MarchApril green/red stems
with red speckles - Branching, hollow, bamboo like stems up to 3 m
high - Extends by rhizomes (horizontal underground
stems) woody with orange-coloured centres
4Identification and Biology
- Oval shaped, smooth edged, alternate leaves (515
cm) - Many small (3 mm) green / white flowers arranged
in dense clusters August - October - Few seeds produced from hybrid unions low
survival - Old growth dies back dormant over winter
- Dead stems and leaf litter prevent establishment
of native seeds
5Growth and Dispersal
- Vigorously competitive tolerant of a wide range
of conditions (soil type, pH, salinity,
temperature) - Rhizomes capable of extending up to 7 m and to a
depth of 3 m - Shoots can grow up to 8 cm/day due to nutrients
stored in extensive rhizome system - Very small fragments (0.7 g) give rise to new
plants - Dispersal occurs primarily via watercourses,
transport routes, waste land, and human activity - No natural competitors
6Problems
- Damage to paving, tarmac, walls, flood defences,
archaeological sites - Reduction of biodiversity
- Restriction of access to river banks / footpaths
- Risk of soil erosion and bank instability
following removal - Increased risk of flooding
- Aesthetically displeasing
7Control Methods
- Can be controlled but requires labour,
persistence and a good understanding of available
methods - Early identification and action is preferable
- Infested soil can not be removed from site except
to landfill license requirements - All knotweed and knotweed contaminated soil
classed as controlled waste under Environmental
Protection Act (1990) Duty of Care Regulations
1991 - It is an offence to plant or cause knotweed to
spread under Wildlife and Countryside Act, 1981 - 5 k fine and/or 6 months imprisonment
8Control Methods1. Dig and Dump
- Digging 3 m deep 7m beyond periphery
- Digging can not be carried out within 10 m of a
watercourse - Burning of material prior to burial is permitted
under an exemption from Schedule 30 of Waste
Management Regulations 1994 - Do not burn actively growing plants
- Required on-site burial depth is 10 m
- Required land-fill burial depth is 5 m
9Control Methods2. Root Barrier Membrane
- Root barrier membrane may be installed prior to
engineered surfaces e.g. tarmac / buildings - Membrane should be large securely sealed
durable UV resistant - Membrane should be placed 2 m or deeper to
minimise damage from burrowing animals
Cell formation using the Dendro-Scott root
barrier membrane
Preventing horizontal spread using vertical root
barrier membrane
10Control Methods3. Mowing or Pulling
- Mowing every 4 weeks or more during the growing
season will slow or halt rhizomes - First cut when first shoots appear last cut
before Autumn die-back - Pulled material should be dried and burned /
buried at the earliest opportunity - Labour intensive small areas / young stands only
- Mowing may encourage spread collecting box
required
11Control Methods4. Grazing
- Formerly used as stock feed palatable to cattle,
goats, horses and donkeys - Introduce animals early in growing season after
June, stems may be too woody - Later introductions require pre-cutting to
encourage tender, palatable shoots - Limited control, no eradication care and
containment of livestock land ownership - Palatable to humans source of Vitamin A/C,
potassium, phosphorous, zinc, manganese,
resveratrol (which lowers cholesterol) and emodin
(natural laxative)
12Control Methods5. Chemical Treatment
- Main herbicides in UK are Picloram, 2,4-D,
Glyphosate, Imazapyr and Triclopyr - Selection based on site location and future
land-use - Treatment must be carried out by a qualified
person under National Proficiency Tests Council - Environment Agency approval required if site is
near a watercourse - Techniques Spraying / Injection
- Herbicides most efficient near flowering stage
- Avoid treating during flowering stage to protect
pollinating insects - Most are ineffective during winter
- Chemical treatment usually requires 3 years
- May force knotweed into dormancy (rhizomes gt 20
yrs)
13Control Methods5.1 Picloram
- Persistent in soil for up to 2 years
- Can not be used near water
- Selective herbicide affecting broad leaved
species, but has little effect on grasses - May be chosen if not replanting or only grass
sward is to be maintained - Can be applied to the soil during winter
Post-treatment reaction to Picloram
Regrowth after Picloram treatment
14Control Methods5.2 2,4-D
- 2,4-Dichlorophenoxyacetic Acid
- Selective herbicide affecting broad leaved
species, but has little effect on grasses - Approved for use near water
- Soil persistence up to 1 month
- Replanting usually possible after 12 months
- Possible human carcinogen
15Control Methods5.3 Glyphosate
- Tradename formerly Roundup under Monsanto
- Method of choice for knotweed control in Rhondda
Cynon Taff County Borough Council - Total herbicide harms all green plant tissue
- Has little or no soil persistence
- Approved for use on or near watercourses
- Low toxicity / environmentally safe
- Replanting usually possible immediately after
treatment - Effects on health and persistence are widely
disputed
16Control Methods6. Biological Control
- Not yet introduced
- Natural population control
- Single clone renders plant more susceptible
- Low costs following initial research phase
- No threat to human health, crop production or
beneficial organisms - Relatively long time-scale (510 years)
17Control Methods6. Biological Control
- CABI Bioscience and Leicester University 2nd
phase of research, 4 year programme - 3 potential agents identified
- Only natural, knotweed specific enemies
considered - Rigorous testing in secure quarantine according
to international protocols - Negligible risk to UK species
18Control Methods6. Biological Control
Stem boring Weevil Lixus sp.
Leaf-spot fungus Microsphaerella sp.
- Sap-sucking plant louse (Psyllid) Alphalara sp.
19Control Methods7. Combined Treatment
- Combining digging and herbicide spraying may
reduce time required for herbicide control - Pre-treatment digging to 50 cm often advised
prior to herbicide application - Rhizome is broken up to stimulate growth
rendering plant more susceptible to herbicide
treatment - Compulsory Digging prior to membrane
installation - Dividing the land and using different techniques
in different areas
20Control Methods8. Do nothing
- No costs involved
- No chemicals involved
- Knotweed spread will continue unchecked
- Associated problems remain
21Costs
- Estimated cost of controlling Japanese Knotweed
in UK is 1.5 bn - At the current rate of treatment (2 ha/yr) the
infestation will take gt50 years without
accounting for its rapid spread - Worst case scenario is a 1 m2 patch costing
54,000 to eradicate prior to building - Aman Valley Greatest concentration of Japanese
Knotweed is along a 1.5 km stretch of road
(Foundry View Incline Row), where the plant
spreads 4 m either side of the road, following
the river - Likely to be additional patches of knotweed
present - Arbitrary costs based on 1500 m x 8 m 12,000 m2
22Aman Valley CostsDig and Dump
- Digger driver 250 / day
- 5 weeks? 6250
- Landscaping costs 8 / m2 96,000
- Excavation 12,000 m2 to 3 m depth 36,000 m3
72,000 tonnes - Landfill tax is 32 / tonne 2,304,000
- NB. This amount can be reduced
- Additional costs associated with licensed
transport / papers - Possible landfill tax exemption only until
December 2008
23Aman Valley CostsRoot Barrier Membrane
- Membrane costs and installation 63 / m2
- Additional costs associated with landscaping 8
/ m2 - Total cost for 12,000 m2 852,000
- NB. Additional costs associated with cutting of
site prior to membrane installation
24Aman Valley CostsPulling / Mowing
- Studies show that it takes up to 2 h to remove a
1m2 area - Cost for pulling 137,520 (minimum wage 5.73 /
hour) - Repeated 4 times / year for 3 years 1,650,240
- Mowing would be quicker and therefore cheaper,
though additional costs incurred through tractor
hire / fuel / maintenance - Additional costs associated with removal / burial
of knotweed
25Aman Valley CostsGrazing
- 12,000 m2 3 acres
- 6 goats per acre 18 goats
- Cost of goats?
- Land ownership winter feed nutritional
supplements - Grazing every year for 3 years
- Livestock fencing labour 6 / m
- 3016 m 18,096
26Aman Valley CostsChemical Herbicide Control
- Spraying costs are 1/m2 8/m2 landscaping
- 12,000 m2 would cost 108,000 / year to treat
with herbicide - Treatment would continue for a minimum of 3 years
324,000 - Quote from EcoControl Solutions, Cardiff for
12,000 m2 140,000 - Advice from Invasive Plant Company, Manchester
suggests above figures are realistic
27Treatment Effectiveness
- Recent investigation into effectiveness of
Knotweed control by Centre for Evidence-Based
Conservation (Kabat et al. 2006) - 6 techniques assessed Glyphosate and Imazapyr
used alone / combination cutting alone cutting
and filling stem with Glyphosate cutting and
spraying regrowth with Glyphosate - No techniques resulted in eradication
- All showed significant short-term reduction
except cutting alone - Lack of robust evidence for long-term
effectiveness - Unable to provide generic evidence-based
management guidelines - Study recommends further long-term research,
monitoring, replication and investigation
28Presentation Title
- What do you think is the best method of control?