Development and application of a biological control programme for the Cassava Green Mite (CGM) in Africa

Background

Cassava is the dietary staple of over 500 million people in some of the world’s poorest tropical and subtropical countries. In Africa alone, over 200 million people depend on this crop for food. Cassava’s versatility in food uses and its adaptability to adverse environmental conditions make it an ideal “safety net” crop. However, cassava is threatened by a number of serious pests. In the early 1970s, an exotic pest – the Cassava Green Mite (CGM) (Mononychellus tanajoa) – was accidentally introduced from the Americas. This spider mite quickly spread throughout the cassava belt, infesting 27 countries in the sub-Sahelian region. By decimating cassava yields, it has become one of the most serious threats to the continent’s food supply. Unfortunately, efforts to control CGM by chemical methods have proven futile.

In 1984, the International Centre for Tropical Agriculture (CIAT) and the International Institute of Tropical Agriculture (IITA), with support from IFAD, initiated a search for natural enemies of this pest, and successfully identified ten promising species of predatory phytoseid mites. In late 1993, a joint IITA/CIAT programme financed by IFAD, the United Nations Development Programme, Brazil, Denmark and Germany achieved biological control using the predator mite Typhlodromalus aripo. Following encouraging trials, the predator was released and produced up to a 50% reduction in pest populations, resulting in 30% increases in cassava yields in eleven African countries. As a consequence, with more cassava available for domestic consumption and sale, food and livelihood security improved.

Grant purpose

The general objective is to develop, test and adapt sustainable cassava plant technologies through a multidisciplinary and multi-institutional effort, and thus increase the productivity of small-scale cassava production systems in Africa.

The specific objectives are to:

• establish a programme to release and monitor proven exotic natural enemies that are adapted to a range of agro-ecological conditions in sub-Saharan Africa;
• integrate farmer participation into research and implementation of CGM biological control through farmer training for biocontrol research; and
• create national capacity for full deployment of biological control technology, including by establishing links with IFAD-financed investment projects targeting producers of CGM-infested cassava.

Components

Diagnostic surveys

Diagnostic pre-release surveys will conducted to collect baseline information on CGM abundance and the prevalence of other pests and diseases and mite pathogens.

Natural enemy propagation and multiplication

Source populations of T. aripo are provided to establish cultures at the national level, to be used for initial releases. In addition, in-field multiplication sites are established with participating farmers.

Natural enemy release and monitoring

Release fields and surrounding areas are monitored for the establishment and spread of exotic predators and mite pathogens. Population dynamics and persistence of predators and pathogens are monitored at selected sites. Countrywide spread surveys will be conducted annually. Non-target impact of predatory mite establishment will be monitored in at least one country.

Integration of biological control into the cassava cropping system

To facilitate the integration of biological control of CGM with host plant resistance to other pests and diseases, research on predator preference for cassava varieties and effect of diseases and other pests on CGM biocontrol will be conducted, and the varieties preferred by the predators will be identified and the information disseminated to researchers, extension workers and farmers.

Farmer participation

Training-of-trainers workshops will be held to provide technical knowledge and facilitation skills on CGM biological control and to enable extension workers and facilitators to produce locally adapted didactic training and extension material specific to CGM biological control. In addition, farmer groups will be trained to handle, propagate, mange and monitor phytoseid populations and pathogen prevalence. Experiments will be conducted in each of the five countries to generate information on the impact that the production practices have on CGM biological control.

Human resources development

The focus is to provide training to enhance national capacity for handling, managing and evaluating natural enemies of the CGM.

Impact evaluation

The impact of exotic phytoseids in different areas will be measured, and the ability of exotic natural enemies to establish and spread will be evaluated. The population dynamics of the pest and the production of cassava in the field will be compared.

Impact

It is expected that the programme will benefits participating and neighbouring countries, with a lower numbers of mite pests and consequent increased cassava yields, leading to enhanced food security, improved incomes and sounder marginal ecosystems. The increased biological control capacity acquired by national programmes could be applied in tackling similar pest problems in crops in the future.

Links to other IFAD projects

• The North-Western Province Area Development Project, Zambia;
• Kagera Agricultural and Environmental Management Project, Tanzania;
• Mara Farmer’s Initiative Project, Tanzania;
• Farmer Field Schools Project in Kenya, Tanzania and Uganda;
• Ghana Root and Tuber Improvement Programme;
• Benin Root and Tuber Improvement Programme;
• Root and Tuber Improvement Programme in Cameroon (pending).

Links to related research results

Centres Declare Victory Over the Cassava Green Mite

Nigeria: Cassava development in Nigeria. A country case study towards a global strategy for cassava development

Contact

Dr. Rachid Hanna
Project Coordinator
Biological Control Centre for Africa
International Institute of Tropical Agriculture
Cotonou, Republic of Benin.
Telephone: INT+229+ 35 01 88
Fax: INT+229+ 35 05 56
E-mail: r.hanna@cgiar.org

Contact in IFAD

Mr Douglas Wholey
Technical Adviser (Agronomist)
Technical Advisory Division, IFAD, Rome