Measuring Plant Diseases

B - Book chapters etc edited externally

Madden, L. V., Hughes, G. and Van Den Bosch, F. 2007. Measuring Plant Diseases. in: The Study of Plant Disease Epidemics American Phytopathological Society (APS). pp. 11-31

AuthorsMadden, L. V., Hughes, G. and Van Den Bosch, F.
Abstract

An epidemic consists of a population of infected individuals in a (generally larger) host population, and the change in diseased individuals over time and space. Before one can understand or compare epidemics, one must first monitor them. We use the Merriam-Webster dictionary and define monitor as: “to watch, keep track of, or check usually for a special purpose.” For the purpose of epidemic analysis, this involves sampling for disease, and measurement of disease in the sample. Measurement is the primary subject of this chapter. Because plant disease involves the interaction of a plant and a pathogen as influenced by the environment, it is natural to consider measurements of plants (e.g., crops, forest trees), pathogens (e.g., spores), and the physical environment (e.g., ambient air temperature) when quantifying epidemics. Depending on the objectives of the study, an investigator may need to quantify variables explicitly representing one or more components of the disease triangle. Different approaches to the measurement of disease may be appropriate for different pathosystems. For instance, measuring a systemic disease caused by a virus may be very different from measuring the area of lesions caused by a fungus on leaves. There are, however, general principles and approaches that apply for all types of measurements, and these are discussed in this chapter. We start with an overview of concepts, and give relevant definitions and explanations of disease, measurement, and some statistical terms. Then, we present a review of common disease measurement methods, and discuss ways to determine the so-called reliability and accuracy of the disease measurements.

Chapter topics include:

Introduction

Plant Disease Intensity

Measurement Levels and Random Variables

Assessing Disease Intensity

Reliability, Accuracy, Agreement

Attributes and Properties of the Crop

Page range11-31
Year of Publication2007
Book titleThe Study of Plant Disease Epidemics
PublisherAmerican Phytopathological Society (APS)
ISBN978-0-89054-505-8
Digital Object Identifier (DOI)https://doi.org/10.1094/9780890545058.002
Open accessPublished as non-open access
Output statusPublished
Publication dates
Print2007

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