Invasive non-native aquatic weeds: an often underestimated problem

Property Care Association - Invasive Weed Control Conference 23rd Nov 2017

By Alex Brook

Ebsford Environmental Ltd

alexbrook@ebsford.co.uk

Invasive Weeds - Legislation

Wildlife & Countryside Act (1981 as amended) - schedule 9 Part II lists:

• 54 plants

• 27 terrestrial – e.g. Japanese knotweed, Himalayan balsam

• 13 aquatic – marine – e.g. giant kelp, green sea fingers

• 14 aquatic – fresh water

EU Regulation (1143/2014) on invasive alien (non-native) species

• 23 plants of concern

• 10 aquatic – fresh water (8 within WCA)

Invasive Weeds – management approach

• Problem identified – what is it?

• Baseline data – where is it? how much? what type of watercourse / body is it?

• Management considerations – environmental, legislation etc.

• Management techniques

• Physical techniques

• Chemical techniques

• Environmental techniques

• Biological techniques

• Data collection & Monitoring

Problem – Invasive Aquatic Weeds

Many different plant Families with adaptations for:

• Living under water

• Living on water

• Growing through water

• Living in water & on land

• Some still / slow water e.g. ponds, lakes, canals,

• Others fast flowing e.g. streams, rivers

Submerged Emergent or Free floating

Marginal / Amphibious

Curly water weed, Canadian & Nuttall’s waterweed

+

Parrot's-Feather + +

Floating Pennywort +

Water Fern +

New Zealand Pygmy Weed + + +

Scale of problems can vary

• Small ponds and streams

• Reservoir infestation e.g. New Zealand Pygmy Weed

• 32 Ha emergent / marginal

• ~ 65,000 m3

A sense of scale

Management Considerations

Environmental

• Biosecurity

• Site designation

• Notable / rare / protected

species

• Fisheries

• Water Extraction

Source: Environment Agency: Aquatic and riparian plant management: controls for

vegetation in watercourses. Project: SC120008/R1

Regulatory

• Env. Impact Assessment

• Waste management

• WFD compliance

• Consent / permissions /

AquaHerb etc.

Other

• Catchment scale

approach

• Flood defence impact

• Partnership working

EA management tool (watercourses)

• A useful tool for watercourses devised

by the EA

• Provides control options

Source: Environment Agency: Aquatic and

riparian plant management: controls for

vegetation in watercourses. Project:

SC120008/R1

Submerged Emergent or Free floating

Marginal / Amphibious

Physical Techniques e.g. Mechanical / Hand Removal

+ + +

Chemical Techniquese.g. herbicides

- - / + +

Environmental Techniquese.g. water level & nutrient management

+ + +

Biological Techniquese.g. Biological Control

- / + + + ?

Submerged

• Canadian* & Nuttall’s waterweed• Introduced 1842

• Perennial

• North America

• Not obvious

• Rooted in sediment

• Only female plant present in GB

• Slow water – ponds or lakes

• Spreads via fragments

• Problems with fishing & reduces biodiversity

J F M A M J J A S O N D

Growing

Flowering

Buds*

Submerged – some options

• Canadian* & Nuttall’s waterweed

Stand characteristics

Large dense infestationSmall infestation

Can the plants be reached with hand tools

YES NO

Hand pulling

Hand pulling /

removal

Mechanical

removal

• No herbicides available

• No specific biological

control

• Mechanical / Cutting /

Shade

• Ongoing management

• Can be controlled with

Grass Carp (requires

agreements from EA)

Submerged & Emergent

• Parrot’s Feather

J F M A M J J A S O N D

Growing / Emergent

Flowering

• Introduced 1878

• South America

• Perennial

• Usually obvious

• Rooted to sediment

• Frost tolerant

• Slow water – ponds or lakes

• Spreads via fragments

• Problems with fishing & reduces biodiversity

Emergent / Floating Matts

• Floating Pennywort

J F M A M J J A S O N D

Growing / Emergent

Flowering

• Introduced 1980s

• South America

• Perennial

• Obvious

• Rooted to sediment

• Frost tolerant

• Slow water – ponds, lakes, rivers & canals

• Spreads via fragments

• Problems with fishing & reduces biodiversity

Submerged, Emergent, Marginal / Amphibious

• New Zealand Pygmy Weed

J F M A M J J A S O N D

Growing / Emergent

Flowering

• Introduced 1927

• NZ & Australia

• Perennial

• Not always obvious

• Rooted to sediment

• Frost tolerant

• Slow water – ponds, lakes, rivers & canals

• Spreads via fragments

• Problems with fishing & reduces biodiversity

Submerged / emergent – some options

• Parrott’s Feather & Floating Pennywort

• No herbicides available

(emergent only)

• No specific biological

control (parrott’s feather),

possible agent for

pennywort

• Mechanical / Cutting

• Ongoing management

Stand characteristics

Emergent

Mechanical

removal

Submerged

Small stand?Small stand?

Herbicide /

removal

Hand

tools

Mechanical

removal

Hand

toolsAccessible?

J F M A M J J A S O N D

Free Floating

• Water Fern

Growing

Spore Production

• Introduced 1883

• N. & Central America

• Perennial

• Obvious

• Free floating

• Slow water – ponds & lakes

• Spreads via individuals & spores

• Problems with fishing & reduces biodiversity

Free floating – some options

• Water Fern

• Herbicides available

(emergent only)

• A specific biological

control available

• Mechanical removal

• Containment

Stand characteristics

Recent infestation and few

plants?

Is the infestation accessible using

hand tools?

Containment /

Physical removal

YES

Containment. Biological control /

Herbicide

An established large

infestation?

NO

Azolla weevil (Stenopelmus rufinasus)

Invasive Weeds – Summary

• Know your problem – the weeds biology

• Data, data, where is it how much is there? – also helps to measure success

• Management considerations – legislation, tick all the boxes

• Management techniques - many appropriate to all, some not so

Physical techniques Chemical techniques

Environmental techniques Biological techniques

• Monitoring

Measures success & detects new infestations

Many aquatic weeds require ongoing monitoring and management, there is no silver bullet!

Manage expectations!