A plant disease model is a mathematical description of the interaction between environmental, host, and pathogen variables that can result in disease. A model can be presented as a simple rule, an equation, a graph, or a table. The output of a model can be a numerical index of disease risk, predicted disease incidence or severity, and/or predicted inoculum development. Note: Plant disease models typically are developed in specific climates and regions around the world. Before using a model that was not field tested or validated for a specific location, the model should be tested for one or more seasons under local conditions to verify that it will work in this location. Models may contain assumptions about site specific conditions that might not apply for all areas. Input variables and/or other parameters such as timing of model initiation may need adjustment due to pathogen biology, host phenology, and variety in a specific area.

Powdery Mildew