Epidemiology: the seasonal carry-over of plant pathogens

Abstract

Epidemiology is primarily concerned with epidemics (more correctly termed epiphytotics in the case of plant diseases), but the term has a wide meaning and has come to include most field aspects of disease. In a sense it is the interaction of crop, pathogen and environment, populations of plants and pathogens rather than individuals being involved. These are the aspects of plant disease which, with control, are of vital interest to all concerned with growing plants for food or commercially. The epidemiology of plant diseases tends to receive less attention than pathogenesis, but a proper understanding of epidemiology is necessary for formulation of intelligent control measures. It covers the seasonal persistence and spread of pathogens, and the effects of environmental factors on their incidence, and is of great importance in disease forecasting. Disease control is an extensive subject and is usually considered separately from, although closely interwoven with, epidemiology. Mathematical analysis has been applied to epidemiology in recent years, notably by Van der Plank (1963), and this promises to be an interesting and rewarding approach to the subject, especially when combined with computer analysis of disease outbreaks. As yet, however, such analysis is based on rather few diseases and its further extension may necessitate revision of some of the conclusions reached.