InoculumPressure

OBJECTIVE

The InoculumPressure component contains models to estimate the time of the disease onset and to derive initial disease severity as a function of the agrometeorological conditions during the non-crop period.

Form about of the InoculumPressure component

RATIONALE

The presence of primary inoculum, which consists of propagules of a pathogen which trigger the start of the disease cycle in the following cropping season (Brown and Ogle, 1997), is a prerequisite for the development of a fungal epidemic (van Maanen and Xu, 2003). The primary inoculum of plant diseases of herbaceous crops usually overwinters or oversummers on perennial weeds or on alternate hosts as mycelium or as spores, and it is carried on the cultivated plant mainly by wind or rain-splash (Agrios, 2005). The modelling of the primary inoculum is crucial for the simulation of a fungal disease, since the epidemic development is influenced by its density, dispersion and type.  Most crop epidemiological models translate the concept of primary inoculum into a value of initial disease severity to initialize the model at the time of the disease onset (e.g., Berger, 1981). Despite this value varies across environments and growing seasons and depends upon the agro-environmental and management factors during the non-crop period, as well as on the disease severity of the previous cropping season (Gupta, 2004), initial disease severity is often kept at a low and constant value or determined by fitting the model according to epidemic measured data (Segarra et al., 2001, Andrade-Piedra et al., 2005).

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