Water hyacinth
Practical Action
initiate such projects because it can take several years for the insect population to reach a
population density sufficient to tackle the pest problem.
In Kenya work is being carried out on the development of a biological herbicide from a locally
found fungal pathogen.
Chemical control
The application of herbicides for controlling water hyacinth has been carried out for many years.
The common herbicides are 2,4-d, Diquat and Glysophate. It has been found that there is a good
success rate when dealing with small infestations but less success with larger areas. Application
can be from the ground or from the air and requires skilled operators. As mentioned earlier the
main concern when using herbicides is the environmental and health related effects, especially
where people collect water for drinking and washing.
Physical control
Mechanical removal of water hyacinth is seen as the best short-term solution to the proliferation
of the plant. It is however costly, using either land-based ‘clamshell’ bucket cranes, draglines or
booms or, alternatively, water based machinery such as mowers, dredges, barges or specially
designed aquatic weed harvesters. Such methods are suitable for only relatively small areas. Many
of these techniques require the support of a fleet of water and land-based vehicles for
transporting the large quantities of water hyacinth which is removed. Mats of water hyacinth can
be enormous and can have a density of up to 200 tonnes per acre (Harley, Julien and Wright,
1997).
Manual removal of water hyacinth is suitable only for extremely small areas. It is difficult, labour
intensive work and in some areas there are serious health risks associated with the work
(crocodiles, hippopotamus and bilharzia in Lake Victoria for example).
Transportation of the harvested weed is also costly, because it has such a high water content.
Chopping can reduce the volume and the water content.
Besides these three mainstream forms of control Harley, Julien and Wright suggest another
method, namely the reduction of nutrient inputs to the water. Although strictly speaking this is a
preventative method, it can be argued that a reduction in nutrients in the water body will result in
a reduction in the proliferation of water hyacinth. In recent decades there has been a significant
increase in the level of nutrients dumped into waterways from industrial and domestic sources as
well as from land where fertilisers are used or where clearance has caused an increase in run-off.
Possible practical applications of water hyacinth
Although water hyacinth is seen in many countries as a weed and is responsible for many of the
problems outlined earlier in this fact sheet, many individuals, groups and institutions have been
able to turn the problem around and find useful applications for the plant. The plant itself,
although more than 95% water, has a fibrous tissue and a high energy and protein content, and
can be used for a variety of useful applications. Below we will consider a number of possible uses
for the plant, some which have been developed and others which are still in their infancy or
remain as ideas only.
Paper. The Mennonite Central Committee of Bangladesh has been experimenting with
paper production from water hyacinth for some years. They have established two projects
that make paper from water hyacinth stems. The water hyacinth fibre alone does not
make a particularly good paper but when the fibre is blended with waste paper or jute the
result is good. The pulp is dosed with bleaching powder, calcium carbonate and sodium
carbonate before being heated.
The first project is quite large with 120 producers involved in paper manufacture. The
equipment for pulping is relatively sophisticated and the end product is of reasonable
quality. The second project involves 25 - 30 people and uses a modified rice mill to
produce pulp. The quality of the paper is low and is used for making folders, boxes, etc.
Similar small-scale cottage industry papermaking projects have been successful in a
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