One of the major problems and causes of difficulties in the control of invasive alien species is that often action is taken too late, only after the weed has spread extensively and the problem has attained huge proportions. It is therefore necessary to stress the importance of making all efforts and take the necessary steps for the prevention of the infestation and - if the alien species is already present - its early detection. This did not happen in the case of Water Hyacinth, Water Lettuce and Water Fern, but should be a lesson for the future.
However, among the means of control, classical biological control is the only sustainable way to control floating aquatic weeds in Africa. The results obtained are encouraging. For instance excellent results were obtained in a short time in the case of Water Lettuce and Water Fern, whose populations were significantly reduced within a few years by natural enemies introduced for this purpose. Water Fern was removed from heavily infested parts of the Senegal River within one year after the release of the biological control agents.
In the case of Water Hyacinth, significant biological control was observed five to six years after the release of Neochetina spp. For instance, following the major project on biological control of this weed in Lake Victoria, five years after the release of the Neochetina weevils the level of infestation was reduced by 60%.
The experience gained to date and the positive results obtained confirm the importance of maintaining the regional approach established by FAO. This cooperative effort should be strengthened and further developed in the future. This approach also requires close international collaboration among institutions and governments. The transnational nature of the problem and the type of territory concerned, where water bodies are even shared among several neighbouring countries, require a global vision and concerted actions for control to be successful.
For this purpose, it is necessary to continue and further develop synergy among stakeholders to (a) maximize efficiency in implementation; (b) optimize the use of resources; (c) allow the sharing of knowledge and facilities; (d) allow the sharing information about levels of infestation, problems and results; (e) prevent reinfestation given the interconnection and the transnational nature of waterways and the fact that often the weed problem in a given country originates in neighbouring countries; and (f) assure continued, coordinated and sustained efforts.
