Augmentative biocontrol of cocoa diseases
United States Department of Agriculture (USDA)
Asociacion de Pequenos Productores de Talamanca (APPTA) and Centro Agronómico Tropical de Investigación y Enseñanza (CATIE) (both Costa Rica), Cooperativa Cacaotera Bocatorena (COCABO) (Panama), Organic Commodity Project (OCP) (USA and Costa Rica), Universidad Nacional Agraria de la Selva (Peru), United States Department of Agriculture (USDA) (USA), Instituto Nigaraguense de Tecnologia Agropecuaria (INTA), Promundo Humano, Global Environment Fund
Measures to date and how successful: Chemical disease control in cocoa has been unsatisfactory. During early development when pods are most susceptible to moniliasis, the pod surface expands rapidly and protective fungicides have to be applied frequently if they are to be effective. Trials with systemic fungicides against moniliasis and witches' broom have also been disappointing. Studies in several countries indicate that fungicidal control of black pod (Phytophthora spp.) in cocoa is economical only if disease incidence exceeds 25-50%.
Thus fungicides alone appear not to be a viable or economic option, and also preclude organic cocoa production.
The main control method available to the smallholder is phytosanitation, and although this reduces losses it is labour intensive. In Peru, weekly and fortnightly removal of diseased pods reduced moniliasis by 35% and 24%, witches' broom by 8% and 6% and black pod by 6% and 3%, respectively. Despite the increased labour entailed by
(the recommended) weekly compared to fortnightly removal, net returns were increased by 33%. However, in Central America, where labour is more expensive, this practice has yet to be validated and adapted for the conditions of each country.
CABI Bioscience input: In January 1997, CABI Bioscience initiated a programme in the Huallaga valley of Peru in which cultural disease control in cocoa was combined with biological control using local antagonists, which had been isoated from cocoa farms in the valley. Since November 1998, this programme has been expanded to CATIE in Costa Rica and Panama. The objective there is the development of biocontrol for the production of certified organic cocoa which is exported to the USA by the Organic Commodity Project (OCP). Trial sites are located in the Talamanca region of Costa Rica and Bocas del Toro in Panama, and these are designed as participatory on-farm trials in collaboration with local NGOs.
Outcome: The success of the project in Peru was marked. Combining cultural and biological control reduced losses due to moniliasis from 100% in abandoned plots and 78% in plots with cultural control alone to 36% in plots treated with antagonists.
In order to design an inoculum which would work under various macro- and micro-climatic conditions and in different production systems, up to five antagonists of different local origins were combined into a mixed inoculum. Biocontrol not only protected the fruit from infection but also prevented the release of M. roreri conidia.
Under field conditions in Peru, Clonostachys rosea (formerly called Gliocladium roseum) reduced moniliasis by 14.6-24.9% compared to optimised, cultural control alone. No significant reduction of witches' broom and black pod was achieved in this trial, but a combination of five C. rosea strains performed consistently best against all three diseases simultaneously. Cocoa yield increased by 16.7% and net returns by 24%. Moniliasis control and yield were positively correlated to the number of mycoparasites in the inoculum. The results suggest that simultaneous biocontrol of the three major cocoa pod diseases with mycoparasite mixtures is extremely promising.
A training manual entitled 'Research Methodology in Biocontrol of Plant Diseases with Special Reference to Fungal Diseases of Cocoa' was published and can now be downloaded free of charge in pdf format from (Resource Centre)
There are also guidelines how to conduct field trials in cocoa at Dropdata.
The recent expansion of the project to Central America means that new biocontrol agent strains need to be isolated and selected, and effective mixtures of them will need to be assessed.
Application systems are to receive increased attention. One avenue to be pursued is a technified IPM approach, drawing on CABI Bioscience's expertise in rational pesticide use. The other will focus on mixed, certified organic production systems on smallholdings. This will follow a participatory research path, accompanied by constant feedback on development needs and technology transfer.
Start date: January 1997
End date: Ongoing