Keywords :

Modelling plant-pest interactions and assessing technical integrated production scenarios

Problems associated with integrated production are especially marked in horticulture. This is an ideal field for designing innovative agricultural systems, which is a major methodological challenge facing agriculture today. The underlying scientific challenge is to clarify functional interactions between horticultural plants and pests under the influence of cropping practices and the genotype, which can reduce attacks or the susceptibility of plants to attacks. The modelling aims to represent these interactions as an ‘intelligent’ system able to react to unexpected technical and genetic scenarios, a broad range of which must be investigated so as to pinpoint ‘breakaway’ scenarios.

We applied these principles to two case studies: a peach-brown rot system, where the pathogen directly attacks the fruit, and a peach-green peach aphid system, where the insect attacks the leaves. On the basis of experimental studies, we modelled the host susceptibility and its modulation by cropping practices, and the direct or indirect effects of pests on fruit quality. The basis of the interaction models was ecophysiological and epidemiological (1st case) or ecological (2nd case).

Technical scenarios simulated via the models, sustained by typical pest control strategies, were assessed through a multicriteria profile corresponding to integrated fruit production requirements. The assessment revealed that: (i) in the peach-brown rot case, scenarios that included water stress provided a good trade-off but required a change in market standards, and (ii) in the peach-green peach aphid case, nitrogen fertilization and pruning could reduce the number of aphids under low pesticide pressure. In further studies, we intend to add genetic components to the models, to increase the scope of the assessments through multicriteria optimization techniques, and to apply these techniques in collaboration with geneticists in order to be able to jointly design plant ideotypes and technical ideotypes for integrated production.