5.1.2S
AN OVERVIEW OF METHODS USED BY TRADITIONAL FARMERS IN DIFFERENT ENVIRONMENTS TO RESTRICT PLANT DISEASE WITHOUT RELIANCE ON EXTERNAL OR SYNTHETIC INPUTS

HD THURSTON

Department of Plant Pathology, Cornell University, Ithaca, NY 14850, USA

Background and objectives
Crop production began perhaps 10,000 years ago. Some ancient farmers developed sustainable agriculture practices that allowed them to produce food and fibre, and to manage plant diseases, for thousands of years with few outside inputs. Many of their successful practices have been forgotten or abandoned in developed countries, but some are still used by traditional farmers in a wide variety of environments in developing countries. The term traditional is usually associated with primitive agricultural systems or pre-industrial peasant agriculture. Traditional farming usually is based on practices that have been passed down for many generations. The objective of this paper is to give an overview of the range of methods used by traditional farmers over time to restrict plant diseases without reliance on external or synthetic inputs.

Results and conclusions
Most of the information on traditional agriculture pertinent to the management of plant diseases has never been recorded in a form easily accessible by today's farmers and scientists. With rare exceptions [1], those who have studied indigenous and traditional agriculture seldom consider or even mention plant diseases. Most practices for disease management used by traditional farmers are cultural practices [2]. Some practices of traditional farmers include the following: altering of plant and crop architecture, biological control, burning, adjusting crop density, depth or time of planting, planting diverse crops, fallowing, flooding, mulching, multiple cropping, planting without tillage, using organic amendments, planting in raised beds, rotation, sanitation, manipulating shade, and tillage [3]. Most, but not all, of these practices are sustainable in the long term. It should be noted that a few of the above practices require high organic inputs, and that some practices have high labour requirements. Some practices have multiple benefits. For example, the use of mulches prevents erosion, improves soil quality, manages weeds, lowers soil temperatures, conserves moisture, and may aid in the management of soilborne diseases. Mulches also reduce rain splashing, an important means of dissemination for numerous bacterial and fungal pathogens. Thus, the use of mulches is increasingly recommended in agricultural development efforts.

The use of disease-resistant varieties emphasizes the value of traditional cultivars (landraces) selected over millennia. Landraces are usually genetically diverse and are adapted to their environment and endemic pathogens. Although they not necessarily high-yielding, they are generally dependable and stable in yielding some harvest under all but the poorest of conditions. Pesticides are generally used only in small amounts by traditional farmers, primarily because of their cost. Traditional agricultural practices should be understood and conserved before they are lost with the rapid advance of modern agriculture in developing countries. Plant pathologists and other agricultural scientists can learn much from traditional farmers to elucidate principles and methods useful in the future management of plant diseases. Traditional knowledge can be overvalued or romanticized, but that is better than despising or ignoring it. Combining the best of traditional agriculture methods with the best of modern agriculture should go a long way towards sustaining agriculture in the coming century.

References
1. Orlob GB, 1973. Ancient and Medieval Plant Pathology. Pflanzenschutz-Nachrichten Bayer 26, 65-294.
2. Palti J, 1981. Cultural Practices and Infectious Crop Diseases. Springer-Verlag, Berlin.
3. Thurston HD, 1992. Sustainable Practices for Plant Disease Management in Traditional Farming Systems. Westview, Boulder, CO.