Incubation

The length of the incubation period is defined as a function of air temperature only. Incubation is calculated according to a modified version of the method proposed by Blaise and Gessler (1992), in which the length of the period varies with temperature through a beta function (Yan and Hunt, 1993), as done for latency.

The temperature response function (f(t), 0-1) is computed with an hourly time step and it is defined as:

where T is hourly air temperature (°C), Tmin, Tmax and Topt are pathogen specific cardinal temperatures for the incubation period (°C).

In the hours when T is below Tmin or above Tmax, the percentage of host tissue affected by the disease does not accumulate thermal time to produce visible lesions.

The hourly progress rate of the incubation period (Inch, hour-1) is then computed as:

where Incumin is the minimum duration of the incubation period (i.e., the duration of the incubation period at optimum temperature).

The four parameters Tmin, Topt, Tmax and Incmin need to be determined for each simulated pathosystem.

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