Operationally, infection models may use hourly or daily weather inputs. The value of W min varied from 1 to 48 h and was relatively uniform for species in the genera Cercospora, Alternaria, and Puccinia but less so for species of Phytophthora, Venturia, and Colletotrichum. Validation yielded an average correlation coefficient of 0.83 and a root mean square error of 4.9 h, but there was uncertainty about the value of the input parameters for some pathogens. The model was validated with published data from 53 controlled laboratory studies, each with at least four combinations of temperature and wetness. The minimum wetness duration requirement ( W min) is the number of hours required to produce 20% disease incidence or 5% disease severity on inoculated plant parts at a given temperature.

The model uses a temperature response function which is scaled to the minimum and optimum values of the surface wetness duration requirement. These inputs are available for many pathogens or may be estimated from related pathogens. The model developed in this study can use inputs based on subjective estimates of the cardinal temperatures and the wetness duration requirement. Most existing infection models require a background epidemiological data set, usually including laboratory estimates of infection at multiple temperature and wetness combinations. The model is designed primarily for use in forecasting pathogens that do not have extensive epidemiological data.

In this study, a simple generic infection model was developed for predicting infection periods by fungal foliar pathogens.

Hyperspaces infection