Capacity Development Portal
Good Practices

Diseases and pests of animals and plants

  1. Biological pest control - example of water weeds
  2. Contingency planning for pests and diseases
  3. Capacity building: the Phytosanitary Capacity Evaluation
  4. Area-wide Insect Pest Eradication with Sterile Insects
  5. Early, community-level disease observation
  6. Networks in disease surveillance and control

Dealing with invasive water weeds by using approaches based on biological rather than chemical control

What problem did it address, where?

Requests have been received from member governments for assistance in addressing invasive water weeds which block water channels used for irrigation, navigation, fishing and combined fish rice aquaculture systems - typical problem species include water hyacinth, water lettuce and water fern. The problem has been experienced most acutely in inland lakes in Latin America, Sub-Saharan Africa and Egypt, where it has threatened local food security, and in rivers in Asia where it was found to be a symptom of a different problem (excessive "run off" of nutrients). Tackling problems with water weeds cannot rely exclusively chemical means otherwise residues can pollute water resources. Biological approaches - identifying and supplying appropriate control agents to feed off invasive species - are an important complementary approach.


Biological pest control has been successfully applied in a number of cases over the years. It involves identifying appropriate control agents, ensuring local understanding of risk (avoiding that the control agents themselves become pests), breeding to supply in sufficient quantities and releasing. The approach works well when infestation levels are not too high (otherwise mechanical removal or chemical means may be needed first); generally the biological control agents are specific to the particular weeds and have been adopted in a number of other countries (reducing the risk of unwanted side effects). The approach requires relatively limited investment, although to be effective the programme must be continued over a number of years (which requires political rather than financial support)

Where next?

Biological control of the same water weeds could be used in new locations suffering infestation, or the approach could be tried (with care) for new weed species.

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