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The control of Water Hyacinth.

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Photo's by Miles Giljam

Manual Control:
People pull out the weed by hand. This can only be effective in small areas and as long as the water is not deep. The advantages of manual clearance it is not harmful to the environment and it does creates job opportunities.

Mechanical Control:

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Photo by Miles Giljam

Excavators are used to pull the Water Hyacinth out of the river or dam. It is a very successful way of clearing the weed. This doesn’t affect the quality of the water but there are disadvantages to using this method:

Machines are expensive to buy.
Machines need fuel to run.
They need to be maintained and one needs money to repair them.
Machines are costly and need to be insured against theft.
You need to employ skilled people to operate the machines.
Machines can damage river banks and property.
Pieces of the plant are not cleared away and the Water Hyacinth will regrow again.

Boats and shredders

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Aquarius at work

These are used in areas where machines cannot reach. They can move into deeper water and the hyacinth is broken up and then using booms it is brought to the shore to be dumped. In South Africa this method is used at Port Owen and in the upper reaches of the Berg river on the West coast. Shredders have been very successful on Lake Victoria in Kenya. 

Mechanical control may be slower than herbicide use, but is selective,
effective, and considered environmentally friendly.

Port Owen dredger collecting water hyacinth with a boom.

The problem is that often there are submerged trees that can damage the boats. The alien vegetation that is found in the Berg river is of particular interest. Hundreds of Blue gum trees are found in and around the river. They provide natural barriers for the water hyacinth to pack and form huge beds of impenetrable growth.

Biological Control:

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Photograph by John Hoffman for Toktokkie Magazine.

e-mail permission to use it from Roberta Griffiths

 

There is a small beetle that has been imported from Australia. This beetle is known as the snout beetle. It is one of the main water hyacinth fighters. It burrows into the spongy stem of the plant which stresses the plant which then sink and die. This beetle has proved to be very effective in the tropical areas. 

Eccritotarsus catarinensis(Heteroptera:Miridae)

This is a sap sucking mirid used in South Africa. The females inserts their eggs into the leaves of the water hyacinth. When the nymphs hatch they eat away at the undersides of the leaves of the water hyacinth. They develop into adults and can live for about 50 days. The adults also feed on the water hyacinth. The leaves turn brown and the plant becomes stressed and dies because of these insects.

Biological control of water hyacinth does not seem to be working well on the West Coast of South Africa . The farmers believe it is because not nearly enough beetles have been sent to this area. The small number released have not bred well and so the impact is minimal.

Chemical Control:
Chemical spraying of crops on the West coast of South Africa

This method is of course very effective. Many different poisons are used including a product called "Roundup"

A very dangerous chemical called 2,4-D has been used to kill off water hyacinth.

When 2,4-D is used, it destroys the Water Hyacinth and everything else in that environment. There is another chemical used called Glyphosate which works much more slowly but it creates less environmental problems.

We do not agree with the use of chemicals as there are many side effects to both the environment and to man.

Did you know?
2,4-D was one of the major ingredients in "Agent orange," This was used in chemical warfare in Vietnam. It destroys and kills plants and trees. 2,4-D has been banned in South Africa, Zimbabwe and Sudan because it is such a health hazard.

Are chemicals being used in your area?

What do you think about the use of Chemicals to control invasive plants?
Let us know!