Vulnerable host tissue

The percentage of host tissue which can be affected by new infections (HTvul, %) is computed on a daily basis  as a function of the total host tissue affected by the epidemic and of the ratio between green and total leaf area index as:

Where GLAI is the green leaf area index (m2 m-2), LAI is total leaf area index (m2 m-2), HTmax is the maximum host tissue which can be affected by the disease (i.e., maximum disease severity, 0-1), HTlat is the latent host tissue (0-1), HTvis is the visible host tissue (0-1), HTspor is the infectious host tissue (0-1) and HTsen is the senescent host tissue (0-1).

HTvul starts to decrease starting from the day of the disease onset.

When the percentage of HTvul is > 0, the new percentage of host tissue which can become infected (HTinf_pot, 0-1)

where Speff is the daily sporulation efficiency (0-1), Crain and Cwind are the efficiency of spore catch by rain or wind,. Infspores is the efficiency of the production of airborne spores by the infectious tissue are computed as:

where HTspor is the sporulating host tissue (0-1) and Drain and Dwind are the efficiencies of rain and wind dispersal (0-1).

The value of Outspores is a critical value because it does not depend from the epidemic development, but it represent the external source of spore production. It varies according to multiple factors (e.g., presence of the same crop in the surrounding fields, presence of alternate hosts). In the current status of development of the DiseaseProgress component, this value is editable and must be calibrated according to specific pathosystems.

The actual value of host tissue which become newly infected (HTinf_act, 0-1) is then computed as

where Infeff is the daily infection efficiency (0-1).

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