Selecting Natural Enemies

Ultimately, the success of any classical biological control campaign rests on finding and establishing well-adapted and effective natural enemies. There is a informed ecological reading, but not much that can be used in a practical way when searching for candidate natural enemies. The challenge is having the foresight to anticipate the biological interactions following an introduction that ultimately make or break a candidate natural enemy.

Rather than looking for natural enemies exclusively based on a set of theoretical characteristics, our foreign exploration efforts in South America initially focused on regions that were agroclimatic homologues to regions in Africa where M. tanajoa outbreaks occurred and high populations persisted on a regular basis (Yaninek and Bellotti, 1987). Within each target region, we looked for the phytoseiid predators found associated with cassava where M. tanajoa was present, especially at low population densities, and screened early candidate natural enemies for their ability to feed and reproduce on M. tanajoa before being considered for importation (Yaninek et al ., 1993).

Collaboration and Training

This campaign could not have been implemented without the contributions of national partners in 20 participating countries in Africa, and international experts from four continents. The campaign foundation was built on a cadre of highly trained and dedicated core staff developed by a small group of biological control specialists recruited specifically for this purpose (Herren, 1989). We recruited and trained local staff to work on basic biology and ecology, natural-enemy mass production and experimental releases, pre- and post-release monitoring, and training. The operational team grew to 35 individuals at the peak of the project. Operational units were supervised by local university graduates with backgrounds in agriculture and biology. Many of these individuals eventually completed PhDs, as part of the programme in most instances.

National collaborators provided the access needed to implement the programme in participating countries. Typically, a key individual was someone with an interest in plant protection who worked for the ministry of agriculture. These individuals made all the contacts and local arrangements required for the programme, including arranging for the import permits to introduce and monitor biological control agents. Since most national programme staff had no experience working with mites of any kind, we routinely arranged subject matter and leadership training for the primary contacts followed by in-country training of programme support personnel (Yaninek and Schulthess, 1993; Yaninek et al ., 1994).

International cooperators provided critical expertise beyond the capacity of project personnel in Africa. This included mitetaxonomy, foreign exploration, international quarantine, selected contract research, and MSc and PhD degree training in some cases. Reliable taxonomic expertise is often hard to come by, but is essential in classical biological control projects. We identified plant feeding and predatory mite specialists as essential collaborators early in the campaign. Foreign exploration by definition was beyond the boundaries of Africa and required cooperators with a local knowledge of cassava, M. tanajoa and their natural enemies. We contracted for foreign exploration to be undertaken by collaborators at Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) in Brazil, and the Centro Internacional de Agricultura Tropical (CIAT) in Colombia. Natural enemies shipped to Africa for experimental releases first passed through quarantine in Europe (initially Imperial College in England, then later the University of Amsterdam in the Netherlands). Universities in Africa, South America, North America and Europe hosted project staff and cooperators for higher degree training and produced 15 PhD, 9 MSc and 9 BSc degrees.

We developed and delivered training in basic acarology and biological control applications as a core activity for participating national programmes. Hundreds of staff and collaborators received in-service training every year. Similarly, bench training was done for 25 national programme collaborators with specialized needs and implemented through a series of internships. Training created the basis for all subsequent research and development activities in collaborating national programmes and is the main reason why the campaign was successful in most countries.

The Costs

Cassava farmers were not the only resource-poor constituents associated with this campaign. Most national programme staff lacked the training, infrastructure, or experience to participate in a campaign like this without significant operational support. Consequently, the campaign generated an estimated US$9.5 million to implement the programme from 1983 to 1997 (Table 5.2). We allocated approximately US$680,000 a year for operations at headquarters, a network of national collaborators that grew to 20 countries, contracted services for foreign exploration, international quarantine and selected research, and training. National programmes needed resources for everything from personnel, basic lab and field equipment, electricity to run the lab, vehicles, fuel, communications, computers, and often the most basic supplies, e.g. pencils and paper. Considering the urgency and scope of the problem, the need for basic infrastructure, and the economic impact of the campaign, the budget was probably a bargain. This investment created expertise, experiences and infrastructure that subsequently benefited other biological control activities in the participating national programmes that far exceeded all expectations (Yaninek and Schulthess, 1993).

Table 5.2. Summary expenditures for core project personnel, operations, foreign exploration, international quarantine, contracts, training and national programmes between 1983 and 1997

Conclusions

The campaign overcame the most daunting challenges to implementation and achieved a number of significant firsts, including the first mite pest on a field crop distributed across a continent to be successfully controlled using introduced natural enemies. This was achieved in spite of the conventional plant protection wisdom at the time because a strong biological, agronomic and economic case was made for a classical biological control solution, and the international donors agreed to support the programme. Long-term support from the donors maintained the campaign momentum, while the network of collaborators and national programme cooperators delivered the programme in more than 20 countries over an initial period of 15 years. Getting the taxonomy right took some effort, but got the campaign off on the right foot, while the prescriptive biology and ecology studies kept us on the right path. These studies directed foreign exploration and candidate natural enemy selection, and helped us evaluate the impact and mechanisms of control by the introduced biological control agents. A cadre of highly trained and dedicated core project staff provided the technical continuity needed for handling and evaluating introduced phytoseiid predators. National programme participants gained training and experience working with mites, and received support needed for the infrastructure and operations required to participate effectively in the programme. Ultimately, the challenges were overcome and the programme achieved its goal of controlling M. tanajoa in Africa using classical biological control. The campaign has had an enormous impact on subsistence agriculture in Africa and created a legacy of biological controltraining, infrastructure and experience that is still evident today.

References pertinent to this module of information are available in the book “Biological Control: A Global Perspective.”