Integrated approaches to understanding and control of diseases and pests in field crops

The idea that there is no such thing as an empty niche became well established in the ecological thinking in the second half of the 20th century. The implications of this ecological concept have been slow to be recognised by plant pathologists and other crop protection scientists despite the fact that they regularly attempt large-scale population management and the prevention of niche exploitation. Two questions that follow from taking an ecological view of crop disease management are what constitutes a niche, and to what extent can decision-makers choose the manner and extent of exploitation of the niche that they wish to protect? It is suggested that in developing IPM strategies, it is important to consider farmers and their wider socio-economic circumstances as part of the niche that is exploited by pests and diseases. This view arises from large-scale studies, in both temperate and tropical crop production systems, of concurrent epidemics of multiple pests and diseases, in which variation in farmers' activities is as obvious as variation in the physical and biological environment. Further incentive for adopting this view comes from the fact that IPM strategies are implemented (or not) through farmers' decisions and actions and so such strategies must be constructed with this filtering process in mind. Methodologies for developing robust IPM strategies are discussed and areas are noted in which further methodological development is needed, including modelling of competition among niche exploiters, formal analysis of adoption of IPM methodology by farmers, and use of information by decision-makers in crop protection.