Integrated approaches to root disease management in organic farming systems

Conventional agriculture has had major environmental impacts, in particular with respect to soil degradation. Soil structure, fertility, microbial and faunal biodiversity have declined, and root diseases are common unless genetic resistance, soil fumigation and/or seed treatments are used. Primarily for environmental reasons and increasing demands for safe and healthy food from the public, farmers have switched over to organic production at an increasing rate. During a transition period of about 5 years, organic farmers may face problems with yield losses and pest or disease problems. However, in well-managed, long-term organic farms, soilborne diseases need not be a problem. Several studies in which disease severity was compared in organic and conventional farming systems (or with soils from those systems) showed that root diseases are generally less severe in organically than conventionally managed soils. The reasons for reduced root disease severity have seldom been investigated, although relationships with nitrogen supply or microbial diversity have sometimes been found. Crop protection in organic farming is generally not directed at controlling particular pathogens or pests but at management of the environment so that plants are able to withstand potential attacks. Resistant cultivars adapted to the local conditions are in demand among organic farmers. However, the main practices that contribute to disease control are long, balanced rotations, organic amendments and reduced tillage, all geared towards maintenance of the soil organic matter content and fertility. Organic farmers can make use of biological control agents and natural toxic compounds in plant extracts. However, these practices are methods of last resort.