Agroecological management of soil borne diseases in tropical horticultural crop by biocidal plants : Hypothesis and chosen methodologies

In Martinique, horticultural crops are likely to be attacked by many soil borne diseases among which major ones are emerging strains of Ralstonia solanacearum that generate high economical losses in cucurbits and solanuceae crops. Simultaneously, nematodes like Meloidogyne sp, Pratylenchus coffeae and Rotylenchulus reniformis constitute the second group of soil borne pests that impact vegetables (tomato, pepper, cucumber, melon, watermelon...), root and tuber crops (yam, carrots) and pineapple. Because of the absence of sustainable chemical solutions, and as horticultural farms extend usually on small areas, long term. rotations with non susceptible crops are not adoptable by local farmers. An enquiry showed that introducing "service" crops with biocidal properties could be an adoptable alternative, provided that these plants fulfil some conditions (easy to install and to destroy, short term cycle...). In order to obtain an agroecological method to control these soil borne diseases, à research program is established to evaluate the efficiency of biocidal plants to be introduced in agroecological cropping systems. The main hypothesis is that by emphasising the cultivated biodiversity through these plants, we could (i) reduce the populations of the targeted soil borne pathogens with biocidal compounds that exudate from roots during the growing phase, and (ii) stimulate other microbial communities that could be antagonists. Both phenomenons may Iead to the acquisition of general suppressiveness, mainly during the phase of decomposition of the service crop, It is however necessary to verify the non-toxicity of these plants and their compounds on useful microbial populations. (Texte intégral