Controlling Aquatic Weeds and Wetland Invaders

This page describes aquatic and wetland invaders as identified in the Tasman-Nelson Regional Pest Management Strategy.

Please note that most aquatic and wetland plants are dispersed by stem or root fragments, so care should be taken when removing such plants to remove all material. Consider carefully what plants you buy for ponds and aquariums. If unsure, check with a Biosecurity Officer. Never dump aquarium contents or water into stormwater drains or water ways.

A brochure containing the information on this page can be downloaded: Controlling Aquatic and Wetland Invaders

Aquatic and Wetland Invaders

Pest Plants

Egeria, or Oxygen Weed

Egeria densa

Country of Origin: South Africa

Total Control Plant Tasman & Nelson Districts.

Difficult to control in water.  If located, please contact a Biosecurity Officer, Ph 03 543 8400.  NPPA Pest plant

AquaticInvaders Egeria

Entire Marshwort

Nymphoides geminata

Country of Origin: Australia

Total Control Plant Tasman & Nelson Districts.

Difficult to control in water.  If located, please contact a Biosecurity Officer, Ph 03 543 8400.

NPPA Pest plant (see back page)

AquaticInvaders EntireMarshwort

Hornwort

Ceratophyllum demersum

Country of Origin: Asia, Africa, Australia, North America

Total Control Plant Tasman & Nelson Districts

Please contact a Biosecurity Officer if you find this plant, Ph. 03 543 8400.

Note: Infestations near Mapua, Tasman and Moutere have been eradicated.   Now thought to only occur in the North Island.

NPPA Pest plant (see back page)

 AquaticInvaders Hornwort

Lagarosiphon or Oxygen Weed

Lagarosiphon major

Country of Origin: South Africa

Containment Plant Tasman & Nelson Districts

Remove: Hand-weed small infestations.  Cover: Cover completely with a weed mat to exclude sunlight.

NPPA Pest plant (see back page)

 AquaticInvaders Lagarosiphon

Parrot’s Feather

Myriophyllum aquaticum

Country of Origin: South America

Regional surveillance plant Tasman & Nelson Districts

Remove: In small ponds, rake up and dispose of plant material. Cover: Cover completely with a weed mat to exclude sunlight. Foliar spray: Spray emergent vegetation, including banks above the present water level. 100ml Glyphosate 360/ 10 litre. Respray regrowth before growth reaches 50mm high. Check periodically and spray regrowth. NPPA Pest plant (see back page)

 AquaticInvaders ParrotsFeather

Phragmites

Phragmites australis

Country of Origin: Temperate zones in both hemispheres

Total Control Plant Tasman & Nelson Districts

Note: An infestation in Murchison has been eradicated.  If located, please contact a Biosecurity Officer, Ph. 03 543 8400.

NPPA Pest plant (see back page)

 AquaticInvaders Phragmites

Purple Loosestrife

Lythrum salicaria

Country of Origin: Europe and Asia

Progressive control plant Tasman & Nelson Districts

Remove: If the infestation is limited, remove individual plants. Foliar spray: 100ml Glyphosate 360 and 10ml penetrant/10 litre.  Repeat applications will be required as this plant is a prolific and persistent seeder.

NPPA Pest plant (see back page)

 AquaticInvaders PurpleLoosestrife

Reed Canary Grass

Phalaris arundinacea

Country of Origin: Mediterranean

Progressive control plant

Foliar spray: Spring to autumn, 100ml Glyphosate 360 and 10ml penetrant/10 litre.

 AquaticInvaders ReedCanaryGrass

Reed Sweet Grass

Glyceria maxima

Country of Origin: Europe

Progressive control plant

Foliar spray: Spring to autumn, 100ml Glyphosate 360 and 10ml penetrant/10 litre. Spray twice during the growth season.

Note: Can be toxic to cattle.

 AquaticInvaders ReedSweetGrass

Senegal Tea

Gymnocoronis spilanthoides

Country of Origin: Mexico to Argentina

Total Control Plant Tasman & Nelson Districts

Note: Infestations in Motueka and Upper Moutere have been eradicated. If located, please contact a Biosecurity Officer if you suspect this plant,  Ph. 03 543 8400.

NPPA Pest plant (see back page)

 AquaticInvaders SenegalTea

Spartina

Spartina species  esturine environment

Country of Origin: North America, England

Total Control Plant Tasman & Nelson Districts

If located, please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

 AquaticInvaders Spartina

Yellow Flag

Iris pseudocorus

Country of Origin: Europe, Asia, North Africa

Regional surveillance plant

Remove: Dig out small infestations, remove all rhizomes. Stem Inject: 5ml undiluted Glyphosate 360 into base of stem. Foliar Spray: 100ml Glyphosate 360 and 20ml penetrant/10 litre. Note: This plant is extremely toxic to livestock.

NPPA Pest plant (see back page)

 AquaticInvaders YellowFlag

Pest Fish

These fish are banned from the Nelson-Tasman region, but are being illegally released here. Please report any suspected sightings of these pest fish to the Department of Conservation or a Biosecurity Officer.

Gambusia or Mosquitofish

Gambusia affinis

Country of Origin: Watershed of Gulf of Mexico

Progressive control pest

Please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

PestFish Gambusia

Koi Carp

Cyprinus carpio

Country of Origin: Japan

Progressive control pest

Please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

PestFish KoiCarp

Perch

Perca fluviatilis

Country of Origin: Europe & Asia

Progressive control pest

Please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

PestFish Perch

Rudd

Scardinius erythrophthalmus

Country of Origin: Europe, Russia and Central Asia

Progressive control pest

Please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

PestFish Rudd

Tench

Tinca tinca

Country of Origin: Western Europe to Asia including Britain

Progressive control pest

Please contact Department of Conservation or a Biosecurity Officer, Ph. 03 543 8400.

PestFish Tench

 Other Aquatic Wetland Invaders

Canadian Pond Weed or Oxygen Weed –

Elodea canadensis

Country of Origin: Canada

Remove: Use trained divers to hand-weed small infestations. 

Cover: Cover completely with a weed mat to exclude sunlight.

Note: This is the only oxygen weed that may be legally sold in New Zealand.  In some situations control may become necessary.

OtherAquaticInvaders CanadianPondWeed

Cape Pond Weed

Aponogeton distachyos

Country of Origin: South Africa

Cover: Cover completely with a weed mat to exclude sunlight.

Foliar spray: Spray emergent foliage 200ml Glyphosate 360/ 10 litre. This plant seeds prolifically.

OtherAquaticInvaders CapePondWeed

Chilean Rhubarb

Gunnera tinctoria

Country of Origin: Brazil

Stump-treat: Cut off leaf stalks and paint stalk stubs with Vigilant Herbicide® Gel or paint with solution of 1 part Triclopyr 600 EC in 20 parts of water.

Foliar spray: 60ml Triclopyr 600 EC and 10ml penetrant/ 10 litre.

Caution: Ensure that spray does not enter water bodies.  If not possible, stump-treat rather than foliar spray.

Note: Seeds spread in flowing water and by birds. NPPA Pest plant (see back page)

OtherAquaticInvaders ChileanRhubarb

Eel Grass

Vallisneria gigantea & spiralis

Country of Origin: Europe, Asia, Africa, & Australia

Remove: Use trained divers to hand-weed small infestations. Very difficult to eradicate.

Cover: Cover completely with a weed mat to exclude sunlight. 

NPPA Pest plant (see back page)

OtherAquaticInvaders EelGrass

Elephants Ear

Alocasia brisbanensis

Country of Origin: Ceylon, Tahiti

Stump-treat: Cut off leaf stalks and paint the cut stalk stub with 1gm Metsulfuron-Methyl 600 and 10ml penetrant/ 1 litre.

Foliar spray: 3gm Metsulfuron-Methyl 600 and 150ml Glyphosate 360 and 10ml penetrant/10 litre.

OtherAquaticInvaders ElephantsEar

Green Goddess

Zantedeschia aethiopica ’Green Goddess’

Country of Origin: South Africa

Stump-treat: Cut off leaf stalks and paint the cut stalk stub with 1gm Metsulfuron-Methyl 600 and 10ml penetrant/ 1 litre.

Foliar spray: 3gm Metsulfuron-Methyl 600 and 150ml Glyphosate 360 and 10ml penetrant/ 10 litre.

Note: Poisonous to humans and stock.  Listed as one of the National Poisons Centre’s top 10 plants, consistently involved in unintentional or childhood poisonings.

Note: White flowered Arum Lily can be similarly treated. 

NPPA Pest plant (see back page)

OtherAquaticInvaders GreenGoddess

Grey Willow

Salix cinerea

Country of Origin: Euorpe, West Asia, North Africa

Stump-treat: Apply Vigilant Herbicide® Gel or paint with a solution of 5gm Metsulfuron-Methyl 600 and 10ml penetrant /1 Litre.  Drill and fill: Drill holes around trunk every 100mm. Fill each hole with 10ml undiluted Glyphosate 360 or 2ml of the solution 20gm Metsulfuron-Methyl 600/1 litre. 

Basal spray: Using X Tree® Basal Herbicide, paint the entire circumference of the lower trunk, for a distance from the root collar, up the trunk to 2-3 times the trunk diameter. 

Foliar spray: Spray ensuring full coverage 125ml Glyphosate 360 and 20ml penetrant/ 10 litre. 

NPPA Pest plant (see back page)

OtherAquaticInvaders GreyWillow

Myriophyllum or Water Milfoil

Myriophyllum variifolium

Country of Origin: Australia

Remove: In small ponds, rake up and dispose of plant material.

Cover: Cover completely with a weed mat to exclude sunlight.

Foliar spray: Spray emergent vegetation including banks. 100ml Glyphosate 360/ 10 litre. Respray recovering growth before it reaches 50mm high. Check periodically and spray regrowth.

OtherAquaticInvaders Myriophyllum

Explanations

NPPA Pest plant: National Pest Plant Accord. Has a list of pest plants banned from sale or propagation throughout New Zealand and is administered by Ministry for Primary Industries.

Dispersal Mechanisms: Most aquatic and wetland plants are dispersed by stem or root fragments, so care should be taken when removing such plants to remove all material.

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Caution in Use of Herbicide and Penetrant Over Water Bodies

Be very cautious in spraying herbicides and penetrants onto vegetation that is emergent from or over water. Always read label instructions on both herbicides and penetrants to note application rates and toxicity to aquatic environments.

Note that Aquakynde is a penetrant with low aquatic toxicity. If foliar spraying is not possible, then consider “stump treat” methods.

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Herbicides Notes

Always read label instructions.

Glyphosate 360

Brand names:

  • Nufarm Glyphosate Gold,
  • Rainbow & Brown Glyphosate,
  • Roundup® Renew,
  • Roundup® 360 pro.

Metsulfuron-Methyl 600

Brand names:

  • Agpro Meturon®,
  • Associate®600WDG,
  • Eradicate 600,
  • Escort®,
  • Matrix™,
  • Meteor 600,
  • Mustang®,
  • Rainbow & Brown MSF600.

Triclopyr 600 EC

Brand names:

  • Agpro Triclop 600,
  • Brush Off®,
  • Eliminate,
  • Grazon®,
  • Rainbow & Brown Triclo Herbicide,
  • Scrubcutter®,
  • Vanguard,
  • Victory™.

Vigilant® Herbicide Gel

Contains Picloram.

X Tree® Basal Herbicide

Contains Triclopyr  and Biodeisel.

Penetrant

Sticking or wetting agent that assists the potency of herbicides.

Herbicide Supplies

Are sold locally at garden centres and farm supply businesses.

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Helpful Websites

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Disclaimer

Information in this fact sheet regarding herbicide does not necessarily appear on the labels of the products concerned. Tasman District Council does not accept liability for any damage to any person, property or thing that may arise from use of chemicals at non-standard rates. Mention of product trade names implies neither endorsement of those products nor criticism of similar products not mentioned.