The insects proved to be the most effective weapon against the water hyacinth, a fast-growing weed that has turned into a major problem on many African lakes and waterways, and succeeded where expensive chemicals and harvesting methods had failed.

Peter Neuenschwander at the International Institute of Tropical Agriculture in Cotonou in Benin, did an economic analysis of the biocontrol of the weed. He calculated the saving on the basis of money saved on more expensive control methods, and improvements to fishing and the transportation of goods.

"Neuenschwander estimates that over 20 years the economic benefits of control exceeded the research costs by a factor of more than 120. And that's ignoring the benefits to the rest of Africa," the magazine added.