La protection agroécologique des cultures

What is agro-ecology ?

On the phytosanitary level, the agro-ecological approach is not new, it was already recommended before the apparition of pesticides, at the beginning of the precedent century. At that time, classical cultural practices were strongly recommended (crop rotations, associations, cultural dates, ...). Today, in the context described above, and being given the progress in knowledge as regards ecology and population management, agro-ecology is to prevent risks of pullulations or infestations, rather than to fight against them or to make them disappear by population management : plants and populations of bio aggressor, following wide scales of time and space. This new way of thinking refers to relatively new fields of studies : agro-ecology, of course, but also landscape ecology, space management, biology of conservation, etc.
Agro-ecologic management is a step towards the valuation of animal and vegetal biodiversity, which also contributes to the good ecological functioning of agro-ecosystems and which is a recognized way of reducing risks of pullulations of pests. By putting emphasis on the management of vegetal planting , cultivated or not (form, structure, height ; arrangement ; composition), the process aims also at the preservation of the beneficial organisms already present, which coincides with one of the directions of biological control. The role of biological corridors for useful fauna is, for example, privileged, both at the local level and at the landscape level.
The agro-ecological approach is not dogmatic: it includes « bio » as well as transgenic and lots of rationalized solutions or of good sense. It promotes the ecological character of the management : chemistry is the last resource while preservation of biodiversity and respect of the environment are privileged. But agro-ecology has also of course the aim of having sustainable products; this approach is thus recommended with an intensive agriculture, aiming at a return to a sustainable ecological equilibrium as well as for more traditional systems while avoiding consequences negative and non intentional of industrial agriculture and adding value to local knowledge, guarantors of a certain ecological sustainability of this type ,of systems.

What is it made of?

One of the privileged agro-ecological techniques for ravagers management is the association of plant species. Apart from a few exceptions, monoculture is today considered as a dead end in a context of reduction of phytosanitary products. In parallel, there is a new interest for multi-species systems, based on the temporal or spatial association of several species for production or, again, of ones specie and one or more species in function of the service. Plant associations tend to favour the action of useful fauna against bio-aggressors, to restore biodiversity and contribute to the return to ecological equilibrium that had been lost.
Finally, the management of plant populations and bio-aggressors populations reveal the three main methodological stakes on the scientific level : integration and “interdisciplinarity” (ecology, agronomy, crop protection, socio-economy, etc) ; the change in scale, local data having to be related to decision-making at a global scale (sloped basin, community, landscape, etc.) ; the taking into consideration of new(and evolutionary) thresholds to the scale of the landscape, taking into consideration at the same time economic criteria (classical tolerance thresholds), social criteria (shared and accepted decisions) and environmental criteria (respect for the environment, preservation of biodiversity, reduction of poisoning risks, etc.).

Jean-Philippe Deguine, CIRAD

Station de Ligne-Paradis

Pôle de Protection des Plantes - 3P
7 Chemin de l'IRAT
97410 Saint-Pierre
Réunion
jean-philippe.deguine@cirad.fr