CROP PROTECTION PROGRAMME Control of Phytophthora megakarya diseases of cocoa with phosphonic acid R7326 (ZA0278) FINAL TECHNICAL REPORT 1 February 1999 – 30 June 2002 Dr Mark Holderness CABI Bioscience (UK Centre) 30 June 2002 This publication is an output from a research project funded by the United Kingdom department for international development for the benefit of developing countries. The views expressed are not necessarily those of DFID. (DFID project R7326, Crop Protection Research Programme). 1 TABLE OF CONTENTS Page Project Summary 3 Executive Summary 5 Background 7 Project Purpose 10 Research activities and outputs 11 Dissemination 34 Project logical framework 36 Contribution of outputs 38 What further research is necessary 40 Pathways whereby present and anticipated future outputs will impact on 41 poverty alleviation or sustainable livelihoods Annexes: 1. Farmer socio-economic survey report 44 2. Technical Report – Implementation of analytical method and 81 Assessment of operator exposure to sprays 3. Technical report – Analysis of phosphonate residues 108 4. Technical report – Analysis of metalaxyl residues 120 2 PROJECT SUMMARY The project was directly concerned with the development and evaluation of an operator-safe fungicide and application technique against a disease of major importance in a crop grown extensively in the high potential systems of West Africa. The programme was particularly concerned with understanding the current issues surrounding chemical use by smallhold farmers in Ghana and with ensuring that application systems are optimized to the benefit of both farmers and consumers. Through an extensive survey across 4 regions of Ghana, the project examined the human and socio- economic constraints to the adoption of disease management technologies among smallholder farmers and identified key issues requiring resolution in the development of effective and viable disease control measures. Through the survey, existing fungicide sprays were found to be considered expensive and very difficult to apply, while few farmers owned the necessary equipment. Cocoa farmers in Ghana were identified as predominantly older people, with cocoa being used to assure a supply of income over a long period of years and with low input, low yield systems. Despite these constraints, fungicide use has clearly increased in recent years in response to the spread of P. megakarya. Long-term field trials conducted in an area affected by P. megakarya showed that stem injection or foliar sprays with potassium phosphonate gave control comparable to that obtained with existing recommendations for metalaxyl + cuprous oxide. As a base commodity, often marketed as a foliar fertilizer, potassium phosphonate is not protected by patent and is likely to be considerably cheaper in product and application than commercial organic formulations. The compound has a markedly lower toxicity than persistent copper compounds. However, experimental modification of formulations reduced but did not eliminate localized phytotoxicity resulting from phosphonate injection, which causes potential issues of acceptability to farmers. A residue analytic capability was established at the Cocoa Research Institute of Ghana and new methods and staff skills successfully developed to monitor phosphite (phosphonate) ions in cocoa tissues. Phosphite was detectable in beans from injected trees, but at levels well below health thresholds. This issue has been extensively discussed with chocolate manufacturers, who are concerned at possible negative publicity from any form of application residue, but recognize also that the phosphite residue is akin to phosphate and may require a different philosophy from that for conventional fungicides. Preliminary work with induced resistance demonstrated some evidence of an indirect mode of action through localized stimulation of resistance compound production by the plant, but significant induced systemic resistance has not so far been demonstrated. Studies on environmental contamination showed that the present foliar spray recommendations and equipment used lead to extensive non-target contamination and wastage. Operator contamination is significant, but does not present a health hazard with the fungicides presently used (although there are implications for similar practices with the more toxic insecticides). While levels deposited are unlikely to lead to significant environmental effects in short-term use, the spray nozzles used are clearly causing extensive wastage of a large proportion of the product applied. Copper compounds are highly persistent and could accumulate in soils over the longer term. Existing spray recommendations were costed at equivalent to 193kg dry bean /ha, unlikely to give a significant return to low-output producers. Comparative cost:benefit relationships are difficult to establish in Ghana as existing recommendations are supported through government bulk purchase and there is at present a mass black pod control programme aiming to provide free applications to all cocoa farmers as part of a cocoa support programme. These relationships also depend on other cultural inputs used and potential yield returns. However, members of the project team sit on the managing 3 group for this national black pod programme and so are able to directly bring project outputs into public practice. The project outputs provided significant progress towards the project goal of improving yields and sustainability of high potential cropping systems by cost-effective reduction in losses due to pests. Project survey work demonstrated a real need and desire among farmers for more appropriate and usable alternatives to existing spray recommendations. Exploration of the use of potassium phosphonate has shown that it represents a viable alternative in efficacy terms and opens up alternative application system options for small farmers. Studies on environmental contamination have shown that current practices lead to extensive off-target contamination and waste, a finding that has significant implications for a large-scale government black pod control programme presently operating in Ghana. These issues require further exploration through participatory research with farmers to determine what is truly appropriate and effective for their use. 4 EXECUTIVE SUMMARY Cocoa is the main commodity crop of Ghana and the country’s second most important export earner, providing livelihoods and revenues for numerous rural communities across the country. However, the recent spread of black pod disease (Phytophthora megakarya) threatens the livelihoods of Ghana’s many cocoa farmers. This damaging disease has spread rapidly westwards across the country and has now entered Côte d’Ivoire, the world’s largest producer. This project set out to explore the implications of potential alternative management measures for black pod disease in Ghana, through a field research programme implemented by the Cocoa Research Institute of Ghana, with advisory and technique development inputs provided by CABI Bioscience (cocoa pathology and induced resistance), Natural Resources Institute (residue analysis and sprayer studies) and University of Reading (biometrics). This was supported by the establishment of analytical facilities and procedures at the Cocoa Research Institute, Ghana to enable analysis of chemical residues within cocoa tissues. Phosphonate and other disease management options were assessed for control of P. megakarya and P. palmivora under different conditions over three successive production seasons. The impact of the disease and farmers’ ability to manage it was assessed through an extensive farmer survey, using participatory appraisal techniques, across 4 regions of the country. Farmers in badly-affected regions reported losing an average of three quarters of their production as a result of the disease in wetter years (i.e. those particularly favouring the disease), with some reporting total crop loss. On these figures, production is reduced to a harvest-only basis, with little prospect of improving production or livelihoods. Farmer surveys under the project have shown that farmers do use considerably more fungicide than was previously the case to manage black pod disease. The disease is spreading westwards into the more productive areas of the country. Because of the central importance of the crop to Ghana’s economic development, the Government of Ghana has recently embarked on an ambitious and expensive centrally-funded programme to provide black pod disease control sprays to all cocoa farmers. There are significant questions as to the efficacy and effects of this approach, which require addressing if inputs are to be optimized financially and environmentally. Existing government recommendations for control with a combination of sanitation and metalaxyl/copper sprays are not being effectively implemented by farmers for reasons of cost and are of marginal benefit in the absence of other inputs. Farmers lack knowledge of the disease cycle and confidence in measures for its effective management. Nonetheless, the proportion of farmers attempting control has increased markedly over the last decade as the disease has become more widespread. The project examined the activity of potassium phosphonate in reducing field disease losses to Phytophthora megakarya and Phytophthora palmivora pod rot. The project has established that use of phosphonate can provide an effective and cost-competitive alternative to existing spray recommendations. Potassium phosphonate is