Urging a natural enmity

Biological pest control is backing the farmers' struggle against those age-old adversaries, mites, locusts and mealybugs. Tunde Fatunde reports

One of the world's leading centres for biological control in agriculture is based in a quiet suburb of Cotonou, capital of West Africa's Republic of Benin. The plant health management division of the International Institute of Tropical Agriculture was set up in 1988 to develop biologically safe ways to eradicate crop pests that threaten sub-Saharan tropical and sub-tropical agriculture.

Its founders, all professional scientists, knew that the success of their goals would be determined by the level of collaboration with university-based scientists and researchers in several continents.

"The biological control programme is a multi-disciplinary, multi-national and multi-continental undertaking, commensurate with the size of the pest problem," said Hans Harren, the institute's first programme director.

For a long time, the widespread and intensive use of pesticides was seen as the most efficient control method for pests which damage crops such as cassava, cowpea, and maize. But insects and other species developed resistance to the pesticides, and the failure of toxic chemical agents and the danger they posed to the environment, led to IITA's introduction of an integrated pest management strategy. Aiming to increase food production and ensure sustained food conservation, the institute strengthened its collaborative research with university-based scientists.

IITA outlined three basic strategic and integrated programmes for pest control.

* the introduction and establishment of pests' natural enemies

* the use of pest-resistant and pest-free varieties of crops

* the modification of the environment of the pest to increase the effectiveness of biological control.

The institute has concentrated on cassava, cowpea, maize and the biological control of locusts and grasshoppers. More than 200 million people in Africa depend on cassava as their major source of carbohydrate, and this plant's leaves, which are eaten as a green vegetable, are a good source of protein. The continuous destruction, particularly of cassava, by pests led a number of countries to seek help from IITA. Two exotic pests from South America, cassava mealybug and cassava green mite, were discovered in Uganda and in Zaire and had spread to West Africa with disastrous effects.

As pesticides proved ineffective in controlling these insects, biological control methods were introduced, and the institute set up the Ecologically Sustainable Cassava Plant Protection in Africa programme (ESCAPP). It is a far-reaching project - more than 500 scientists applied to the programme - and it has involved scientists and social scientists from various universities working in joint research, using multi-disciplinary approaches.

Researchers who worked with the IITA scientists were drawn from Imperial College, Wye College, Simon Fraser University in Vancouver, Laval University in Quebec, University of California, Berkeley, University of Sao Paulo, Brazil, the universities of Amsterdam and Leiden, Netherlands, the Federal Institute of Technology, Zurich, the University of Negev, Israel, the National University of Benin Republic, and Omar Bongo and Ibadan universities in Nigeria. The huge effort has largely succeeded. Sixty natural "enemy" species were identified as capable of neutralising the damaging effects of the two pest species. Fifteen of these species are being bred in the institute's central laboratory, for use on farms.

An independent study published in the American Journal of Agricultural Economics estimated the benefit to African farmers from the mealybug campaign to be about $3 billion, "Enough to cover IITA's operating budget for 150 years", says Dr L. D. Stifel, IITA's former director general.

Donor countries, especially from the advanced industrial economies, have agreed to fund other research programmes coordinated by the institute. One is the biological control of locusts and grasshoppers. Following a plague of locusts in the savannah region of Africa from 1986 to 1989, crops planted by farmers were destroyed and the region suffered an unprecedented economic disaster.

Chris Lomer, an entomologist from Britain, led IITA's locust project, involving four donor countries (including Britain through the Overseas Development Administration) which provided financial help. Scientists from the University of Wales, Cardiff, South Bank University, University of Bath, and four universities in West Africa, collaborated to produce the fungus Metarrhizium flavovirid, known to be effective at combatting the destructive insects. "Field trials showed that Metarrhizium, an entomopathogenic fungus, can control the variegated grass-hopper, the rice grasshopper and some other Sahelian grasshoppers. Trials showed mortality occurring six days after application. After 10 or 12 days, between 70 to 90 per cent of the grasshoppers were killed," Dr Lomer said.

In 1994, the Swiss Development Corporation provided IITA with funds to carry out research on the biological control of pests which attack another important crop, the cowpeas in sub-Saharan Africa. Scientists at IITA, headed by Manuele Tamo, an insect ecologist, are now carrying out research with scientists from the University of Wageningen (Netherlands), Universitat Hohenheim (Germany), University of Laval, University of Ghana, and the University of Science and Technology at Port Harcourt, Nigeria.

Peter Neuenschwander, an entomologist and director of IITA Cotonou, said: "Resistant progenies of wild cowpea coupled with cultivated cowpea crosses were made by producing some genes resistant to the predators which attack the plant. And three parasitoid resistant strains are being grown under quarantine conditions at the University of Wageningen."

Pre- and post-harvest losses of maize to pests have also attracted research attention. Fritz Schulthess, an ecologist, and Kitty Cardwell, a plant pathologist, are working with scientists from Texas A&M University, Universidad Autonomo de Mexico, Simon Fraser University, Universitat Hanover, and the University of Cape Coast in Ghana.

They have released two exotic natural enemies of two different maize pests. And Setamanou Mamoudou, a post-doctoral fellow from Universite du Benin, has won an award from the African Association of Insect Science for carrying out original research on the menace posed by a maize pest.

One of the institute's objectives is to work with universities to train African entomologists and pathologists at master and doctorate level, so that eventually they will become experts in integrated pest management. Each year, more than 100 graduate research students conduct projects under the supervision of IITA scientists and their colleagues in universities of Europe, Africa and the Americas. The US-based Windrock International, a privately-financed agency, provides financial help to train women researchers.

However, it is not all plain sailing. Rising costs and diminishing funds have cut the number of African graduate students at European and American universities. And the closure and interruption of research, with the exodus of teachers from many highly-rated African universities, is hindering IITA's postgraduate training.

The institute and several South African universities are discussing ways to back postgraduate training for African entomologists and pathologists. Dr Neuenschwander said: "Despite the cut in funds, I believe the institute's research collaboration with the universities will continue to have an impact on agricultural products."