CABI Bioscience, Bakeham Lane, Egham, Surrey TW20 9TY, UK

Background and objectives
For resource-poor farmers in Asia, crop health is a major constraint to improved crop yields and quality. Insect and nematode pests, diseases and weeds can all affect crop yield and the quality and appearance of produce which, in turn, affects the food security and income of farm families. Farmers grow a number of crops and varieties in different cropping systems and are confronted by complex pest and disease management decisions. It is often particularly difficult to diagnose and understand plant disease problems and soilborne problems such as nematodes. Ineffective, conventional extension and the inappropriateness of messages emanating from research in national and international programmes mean that farmers cannot access the information they need to manage crop health problems. Furthermore, this lack of knowledge makes farmers vulnerable to the promotion of chemical pesticides which can appear to offer simple solutions. CABI Bioscience is pioneering the development of participatory methods for farmer training in pest and disease management, taking a systems approach and building on the farmer field school model used by FAO for rice in Asia. These methods have at their heart the belief that practical IPM in developing countries must stay close to farmers and allow farmers to 'own' the knowledge of IPM themselves.

Materials and methods
Farmer field schools help farmers, through discovery, to learn about field ecology and integrated crop management. Ultimately farmers are able to make and evaluate their own crop management decisions. The schools are run by trainers who, themselves, undertake a season-long training in the field, learning first-hand about the problems that farmers face throughout a cropping season. Although there are no standard recommendations or packages of technology offered, trainers and farmers combine their knowledge to devise testable, risk averse crop management practices to suit their differing requirements. In the farmer field schools, farmers evaluate preventative measures against diseases and, where appropriate, take remedial action against insect pests based on observations in their own fields. Conservation of natural enemies and other beneficial organisms is vital. Biopesticides rather than chemical pesticides are applied only in case of emergency or when no other management methods are available. Discovery-based exercises are an important part of the field school programme and assist farmers in understanding key concepts such as disease cycles, pathogens, biological control, pest life cycles, crop nutrition and compensatory capacity.

Results and conclusions
Participatory methods to improve the diagnosis and understanding of plant diseases and nematodes have been devised and implemented within a broad curriculum. The systems approach, integrating all aspects of crop and resource management, has been vital to the improvement of crop health in low-external-input systems. However, disease management options, which employ mostly preventative, tolerance or avoidance measures, can give rise to conflicts in the use of resources, e.g. whether to burn, compost or feed crop residues. Furthermore, the benefits to farmers in low input systems in terms of yield and quality are likely to accumulate slowly over several seasons. The farmer field school model is a useful template for farmers to evaluate different practices in their own fields. It is a powerful vehicle for the extension of well understood practices, such as seed cleaning and nursery sanitation, but it is clear that farmer participatory research is required to develop more detailed guidelines for other measures.