To study the interest and the limits of the insertion of various cover crop with biofumigation potential in a crop succession, three trials, one in Aquitaine (40), one in Normandy (50) and one in Rheu (35) were performed on two important soilborne diseases of carrot: cavity-spot due to Pythium sulcatum or the brown rot disease due to Rhizoctonia solani. Intercrop plants were cultivated then crushed and incorporated in the soil one month before carrot crop. In the three trials, the effect of the mustard Brassica juncea on the incidence and the severity of the diseases is studied and compared with bare soil. In the Normandy trial, two other cover crops are also studied: oat and rye crop. In Le Rheu trial, regular observations allow to compare the development of cavity-spot over time after insertion then incorporation of a mustard crop or after a bare soil. The results are presented; the technical feasibility and the impact of method on disease development are discussed.
