Agriculture Reference
In-Depth Information
temperature and wetness on short time-scales (one hour or less) and the development
of forecasting models.
The monocyclic phases of all the pathogens considered have been modelled, for
example, the effect of temperature and wetness period on rust infection (de
Vallavieille-Pope
et al
., 1995, 2002), or the influence of temperature on latent period
(Zadoks, 1961). Also, the effect of inoculum or lesion density on monocyclic
parameters has been investigated (e.g. Damgaard and Østergård, 1996; Robert
et al.,
2004), as well as global epidemics as functions of time under the influence of
climatic factors (e.g. Coakley
et al
., 1988). It seems that it would now be useful to
combine qualitative and quantitative parameters and to analyse the effects of
climatic factors on the whole epidemic using analytical models (Hau, 1990) or
simulation models, combined with a growth model of the host. A first step in
combining qualitative and quantitative parameters has been achieved by taking into
account aggressiveness parameters as well as virulence frequencies (Villaréal and
Lannou, 2000; Lannou, 2001). The next step would be to include the effects of
climatic factors on each phase of the infection cycle and to integrate the spatial
spread of epidemics.
The quantification of disease parameters has made it possible to perform
prospective studies to predict disease risks. Forecasting is now possible to optimize
fungicide treatments, but another purpose is to suggest methods to select for disease
resistance and to manage resistance genes. For example, such advances permitted
simulation of slow rusting or slow mildewing epidemics and proposals for
exploiting resistance gene diversity in geographic areas and variety mixtures.
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