Invasive weeds: Guidance for the control of invasive weeds in or near fresh water

Parrots feather

Fact file

Parrots feather (Myriophyllum aquaticum) is a native of lowland central South America. It was first found in Britain in 1960 and has now spread to about 150 sites. It grows in ponds, reservoirs, gravel pits, streams, canals and ditches, particularly where eutrophic water occurs. It can grow as a terrestrial plant when a pond dries out, and has even been found growing on the dry bank of a rubbish tip in Cornwall. It produces emergent shoots in addition to submerged ones, which give it the characteristic feathery appearance, hence its name.

Only female plants are established in the UK and it therefore spreads by vegetative means only. The stems are brittle and the plant propagates by growth from small stem fragments. The species is attractive to look at and is widely grown in garden ponds. Introductions to the wild are usually not deliberate, but fragments can be concealed in the soil of other pot plants sold at aquatic garden centres and nurseries.

Source: Biological Records Centre

Control

Chemical control can be achieved by applying dichlobenil in spring to shallow water and to areas of damp ground. Applying diquat to emergent leaves and stems at 25 l/ha (only permitted until June 2004) during the growing period will also give good control. Glyphosate is less effective on this species, unless used with an approved wetting agent.

Cutting and dredging can be used very effectively in small areas, but all fragments should be removed to prevent regrowth and downstream spread.

Non-chemical control

Cutting

Cut material must be removed from the water as soon as possible. Fragmentation must be avoided. Material should be cut as often as necessary and at least every six to nine weeks from March to October to weaken the plant.

Pulling or dredging

Dredging shallow areas will remove this plant very effectively.

Carefully pulling out stems by hand after mechanical removal will help to eradicate it.

Grazing

The plant is not palatable to herbivores; cattle and horses will avoid it. There is virtually no insect damage to plants in the UK, but research into biological control agents is under way.

CONTACT THE ENVIRONMENT AGENCY FOR DISPOSAL ADVICE

Chemical control

Emergent

Submerged

In general

Apply glyphosate at 6 litres/ha to emergent stands from March to October. Regular annual treatment is required, and at least two applications will be necessary each year.

Treat submerged material with Reglone throughout the year. Submerged parts will die if the emergent portion has been regularly sprayed with glyphosate. Treatment usually lasts for three to five years.

Regular treatment is necessary. Weed wiping may be appropriate in mixed marginal vegetation. Spot treatment of small patches will prevent complete dominance. Treat early and regularly.

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