Nigeria Content Online

Researchers have
released two species of weevils to eat up the water hyacinth in River
Mono, Republic of Benin. The weevils – Neochetina and N. Bruchi – are
special species of weevils that feed on water hyacinths only.

Obinna Ajouno, a
scientist with the International Institute of Tropical (IITA) who is
also a member of the research team, said the two biological agents have
proved to be effective control agents of the water weeds.

Water hyacinth
(Eichhornia crassipes) often grows as floating plants or mats, as
islands of plants floating freely on the water, or mixed with other
vegetation on river banks.

It is expected that
the project, if adopted in Nigeria, will tackle the devastation caused
by the water weed and free waterways for fishing and transport. It will
also drastically reduce the cost of removing water hyacinths from
Nigerian waterways, which is estimated to cost the country up to N1
billion annually.

The released
weevils were mass produced by the Department of Agriculture in
Porto-Novo, using start-up colony supplied by IITA, which also provided
technical assistance.

“Previous efforts
by IITA and partners using bio-control agents against water hyacinth,
yielded success on the Oueme River eight years ago,” Mr Ajouno said.
“However, the use of the weevils is the first of its kind. We are
confident this approach will produce results.”

The project is part
of the ongoing African Development Bank (AfDB), funded ECOWAS
integrated project for the control of aquatic weeds involving physical
removal, utilisation and biological control methods.

Participants in the
project, which was initiated on July 30, 2010, included the Department
of Agriculture, the National Coordination Unit of the Benin ECOWAS
Water Weeds Project, the local communities and IITA.

Godwin Atser, the
West African public communications officer of IITA said the success of
the project will rub off on other ECOWAS water ways including Nigeria.

“In nutrient-rich
waters such as in polluted ponds or lakes, it can grow so quickly that
the surface covered by the mats doubles every four to seven days,” Mr
Ajouno said.

Destructive weeds

The aquatic weed
poses serious socioeconomic and environmental problems to millions of
people in riparian communities and limits development. For instance,
the Nigerian government budgeted N400 million in the 2009 budget to
clear the water hyacinth in Port Harcourt waterways only.

The weed obstructs
electricity generation, irrigation, navigation, and fishing; increases
water loss resulting from evapo-transpiration; and facilitates
proliferation of such diseases as bilharzia.

In Sudan alone, a
partial evaluation of socioeconomic costs of water hyacinth estimates
that annual water loss from evapo-transpiration over 300 km2 of canal
would be enough to irrigate more than 400 ha. Effects on navigation in
the Nile include 50 per cent higher running and maintenance costs and
30 per cent more use of fuel.

The cost of chemical control alone, over 15 years, would have been
in excess of $19 million, according to the International Development
Research Centre (IDRC). Until 2000, the Mono River which borders Togo
was free of water hyacinth. Researchers are of the view that the weed
might have been infested through human activities. But Mr Ajouno says
the impact of these biological agents-(weevils) – in the Mono River
system in the years ahead will be monitored by regular field visits
involving the collaborating institutions.