A biological control programs initiated by the International Institute of Tropical Agriculture and partners on cassava green mite have brought benefits worth more than $1.7 billion to Nigeria, Benin, and Ghana in the last 18 years.
Ousmane Coulibaly, IITA Agricultural Economist describes the figure as “a conservative estimate.”
“The figure represents the amount those countries would have spent over the years on other methods such as chemical control and or yield losses if they never adopted biological control,” says Coulibaly.
The cassava green mite is a pest that was responsible for between 30 and 50 percent yield loss of cassava in Africa, until a natural enemy of the pest helped contain the devastation.
In 1993, scientists from IITA and partners identified, Typhlodromalus aripo, as one of the most efficient enemies against cassava green mite, and the introduction of T.aripo reduced pest populations by as much as 90 per cent in the dry season when pest populations are usually high. In the wet season, pest attacks are not as severe.
T.aripo was first released on cassava farms in Benin after it had been transported from Brazil and, subsequently, in 10 other countries where, except Zambia, it is now confirmed as established in all of them.
T. aripo has also spread into Togo and Côte d’Ivoire from neighbouring countries. It spread at about 12 km in the first year, and as much as 200 km in the second year. Today, the cassava green mite predator has been established on more than 400,000 square km of Africa’s cassava growing areas.
The IITA scientists said the control of the pest through the application of toxic chemicals was ruled out because of possible adverse effects of chemicals on illiterate farmers and the environment. Also, disease pathogens and pests tend to gradually develop resistance to chemical pesticides over time.
Moreover, most chemical pesticides are not selective and might destroy the natural enemies and the pests together.
Coulibaly noted that since the release of T. aripo, benefits to Nigeria have been estimated at $1.367 billion, followed by Ghana $305 million, and Benin $54 million.
Consumed by more than 200 million people in sub Saharan Africa, cassava is a staple food that is rich in calories, highly drought tolerant, thriving in poor soils and easy to store in the ground.