The measurement of plant disease and its effect on crop yields

Abstract

The measurement of plant disease and its effect on crop yield, quality and value are crucial both for the establishment of priorities for control and for the evaluation of any control measures that may be instituted. Unfortunately, this area of plant pathology has proved to be one of the more intractable. For example, Spadafora and co-workers (1987) stated that, ‘A major impediment in the evaluation of control programmes for Leptosphaeria nodorum (anamorph Septoria nodorum; an important parasite of wheat) is a lack of quantitative information regarding relationships between disease severity and yield losses’. Ideally, one would like to be able predict the yield and quality of a crop in the absence of disease and in its presence at several levels of severity as well as the probability of the disease progressing through these levels during the growing season.