Researchers have found two species of beetle to be a potent weapon in Africa’s fight against water hyacinths, an aquatic plant indigenous to Brazil that has become a devastating superweed.
A team of scientists, led by Peter Neuenschwander at the International Institute of Tropical Agriculture in Benin, west Africa, has carried out the first detailed study into attempts to ”bio-control” the weed using two weevils, Neochetina eichhorniae and Neochetina bruchi, which eat water hyacinths and, so far as is known, nothing else.
Neuenschwander estimates that in southern Benin alone the economy has saved $260-million since the two weed-munching species were introduced in 1991 and 1993.
Their study is to be reported in an upcoming issue of Britain’s New Scientist magazine, and has been published in full in the specialist journal Ecological Economics.
The research, based on interviews with 320 people in nine villages, says the beetles have also been beneficial in hidden ways, providing indirect spin-offs to the economy as well as improving water quality and human health.
Water hyacinth, introduced in the 19th century by misguided horticulturalists, is a serious menace in many parts of Africa.
It comprises floating mats of weed that can double in size in less than two weeks, making fishing and boat transport almost impossible. Crododiles like to lurk under its cover, making it hazardous for local people to collect water.
The weed also sucks oxygen out of the water, increases its acidity and slows down currents, adding to silt in the waterways.
Efforts to destroy the weed using machinery have proved futile.
Chemical pesticides do work but they also pollute the water and kill other plants.
N. eichhorniae and N. bruchi can cut coverage by 90% in areas where they are introduced.
The beetles were first introduced in Sudan and have proved so successful that they have been deployed across Africa. But until now there has been only anecdotal evidence as to their impact. – Sapa-AFP