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Although the exact nutrient threshold below which E. crassipes will not flourish is not yet clear, it is certain that its vigour is directly related to available levels of nitrogen and phosphorus. Wherever possible, nutrient levels in the water body should be reduced or controlled: for example, by processing sewage or other nutrient-rich water, or by diverting it away from critical areas In South Africa, Coetzee and Hill (2012) suggest that the first step in any control programme should be to reduce the nutrient status of the water body, as a meta-analysis of studies that investigated the combined effect of P and nitrogen (N) water nutrient concentration and control agent herbivory showed that water nutrient status was more important than herbivory in water hyacinth growth.
Where E. crassipes is causing the most acute problems (e.g. impeding access for fishermen, or threatening to block harbours or damage hydro-electric installations), an effective solution may be the use of floating booms or fixed barriers to prevent movement into the critical areas. Booms may also be used to try and prevent movement of the weed down rivers, though their success will depend on their design (complicated by the need to maintain navigability along the river), the mass of material involved and the capacity to clear the booms by physical removal of weed.
Physical removal or destruction of the infestation may be achieved on a small scale by manual removal. On the larger scale, machinery is needed, either shore-based, or mounted on boats. Where possible, on smaller water bodies, reliance should be placed on unspecialized shore-based equipment (e.g. drag-lines, excavators, moving-belt elevators etc.), the weed being pushed to the shore by suitably modified boats. For larger water bodies, special boats may be needed with suitable harvesting equipment, together with a means of crushing the weed or otherwise reducing the volume of water. Where the water body is sufficiently large and deep for the weed to be returned to the water after crushing, without risk of decomposition causing deoxygenation, the use of such equipment may be economic. If the weed has to be transported to the land for unloading, the running costs become much greater and such methods may not be economic.
Julien (2008) reviews biological aspects of E. crassipes related to management, and suggest that containment and eradication from a catchment may only be accomplished if the invasion is very young, small, isolated and accessible, and if the short-term resource commitment is high. Jyoti and Garima (2013) present methods of control including manual pulling and harvesting.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources: