Biocontrol offers benefits to Africa

Biological control programs implemented by IITA and partners on cassava green mite have brought benefits worth more than $1.7 billion to Nigeria, Bénin, and Ghana in the last 18 years.

Diseased plant. Photo by IITA.
Diseased plant. Photo by IITA.

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,” said Coulibaly.

The cassava green mite is a pest that was responsible for a yield loss in cassava in Africa of between 30 and 50% until a natural enemy of the pest helped to contain the devastation. In 1993, scientists from IITA and partners identified Typhlodromalus aripo as one of the most efficient enemies against cassava green mite. The introduction of T. aripo reduced pest populations by as much as 90% in the dry season when pest populations are usually high; in the wet season, pest attacks are not as severe.

T. aripo from Brazil was first released on cassava farms in Bénin and, subsequently, in 11 countries; it is now confirmed as established in all of them, except Zambia. T. aripo has also spread into Togo and Côte d’Ivoire from neighboring countries. It spread to about 12 km in the first year, and as much as 200 km in the second year. Today, the predator of the cassava green mite has been established on more than 400,000 km2 of Africa’s cassava-growing areas.

Scientists say chemical control of the pest was ruled out because of possible adverse effects of chemicals on illiterate farmers and the environment. Also, disease pathogens and pests tend to develop gradual resistance to chemical pesticides over time. Moreover, most chemical pesticides are not selective and might destroy the natural enemies and the pests together.

Coulibaly notes that since the release of T. aripo, benefits in Nigeria have been estimated at $1.367 billion, followed by Ghana $305 million, and Bénin $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.

2 thoughts on “Biocontrol offers benefits to Africa

  1. I would like to introduce myself as Dr. C.A. Jayaprakas, Principal Scientist (Entomology) and Head, Division of Crop Protection, Central Tuber Crops Research Institute (CTCRI) (Indian Council of Agricultural Research) Thiruvananthapuram, Kerala, India. CTCRI is the only institute in India dedicated exclusively for research on tuber crops, particularly on cassava.

    I have been working on various aspects of the pests of cassava and other tuber crops for the last 23 years. It is interesting to note that Typhlodromalus aripo is an efficient predator of cassava green mite. In India the cassava is infested by four spp. of mites viz. Tetranychus telarius L., T. neocaledonicus Andre, Eutetranychus orientalis Klein, and Oligonychus biharensis (Hirst).

    Do you have any observation/ report on the predatory nature of Typhlodromalus aripo on the four species I mentioned above? Papaya mealy bug, Paracoccus marginatus, is the major problem in cassava and a number of other economically important crops here, but this has been managed well by a phytochemical formulation developed by me.

  2. Dr Jayaprakas
    We do not have direct information on the effects of T. aripo on the four species you have on cassava, but it can develop and reproduce – but poorly – on species (Tetranychus urticae and O. gossypii) closely related to those you have in your system. Please refer to the publication byGnanvossou et al on prey mite an life history of phytoseiids Exp Appl Acarol v30 pp 265-278. I will send you a pdf of this publication by e-mail. On the basis of results of the studies reported in Gnanvossou et al. 2003, I suspect that T. aripo will not do well on the tetranychid mites in your cassava system. It may be however good for you to introduce T. aripo and test it under your conditions. The added benefit of this is that this predator is excellent against cassava green mite, which you do not have in India, but could invade sometime in the future. Having T. aripo already in India may very well reduce the chances of invasion and establishment of cassava green mite in India.
    Hope this helps.
    Rachid Hanna

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