Keywords :

OMEGA 3 project–ecological mechanisms of pest and disease management optimized to sustainably improve agrosystem productivity

High specific plant diversity (DVS) is typical of natural ecosystems, which are affected to a much lesser extent by biological attacks than cultivated ecosystems. Such attacks are generally (but not always) controlled when DVS is introduced in these latter ecosystems. CIRAD, in collaboration with its partners in tropical regions, is analysing the impacts on pathogens of enhancing DVS in agrosystems under various spatial and temporal conditions, in order to determine ecological regulation processes that could be utilized to reduce the need for chemical pesticide treatments.

The following factors are studied over a range of pests and diseases (differing in terms of their host specificity and dispersal capacity), plants and DVS implementation conditions and scales: allelopathic effects of cover crops on white grubs and Striga infecting rainfed rice in DMC systems in Madagascar; allelopathic effects and disruption of the sanitizing plant cycle in rotations on bacterial wilt of tomato in Martinique; the diversion effects of trap plants on tomato moths in Niger and Martinique; the diversion effects of a food-biological insecticide attractant mixture on cucurbit flies in Réunion; the effects of woody species associations on mirid bugs and black pod rot of cocoa in agroforestry systems in Cameroon; and the effects of landscape fragmentation on coffee leaf rust and berry borers in agroforestry systems in Costa Rica. Experimental studies on these suspected effects have already generated several results. Based on formalization of the studied ecological processes, decision rules could be drawn up to develop mechanistic models to predict the impacts of DVS enhancement on pests and diseases according to their life cycle traits—which is a prerequisite for developing innovative pest-resistant cropping systems.

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