Latency

The length of the latency period depends on external variables (mainly temperature and relative humidity) and on the host (e.g.: cultivar, age, etc.).

In the current implementation, latency is defined as a function of air temperature only. It 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).

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 latency period (°C). In the hours when T is below Tmin or above Tmax, the percentage of host tissue does not accumulate thermal time to become infectious.

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

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

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

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