Effect of maize crop residue density on Fusarium head blight and on deoxynivalenol contamination of common wheat grains

Fusarium head blight (FHB) of small grain cereals is a worldwide disease that reduces yield and causes deoxynivalenol (DON) contamination in grains. Non-decomposed residues from the previous crop present on the soil surface are considered the principal inoculum sources for Fusarium graminearum and F. culmorum, the most important Fusarium species that cause FHB in Europe. The objective of this study was to investigate the effect of the amount of previous residues on the FHB disease under natural conditions and on DON contamination in soft wheat following grain maize. Field experiments were conducted in two cropping seasons and two sites to compare four maize residue densities on the soil surface and in the first 10 cm of soil in tilled and non-tilled fields. Ploughing to a 30 cmdepth significantly reduced FHB severity (by 63%) and DON occurrence (by 80%) in each year and site. FHB severity and DON contamination significantly increased with the density of the residues left by the preceding crop. This study confirms that conservation tillage may increase DON concentration in wheat grain compared to ploughing which buries residues. This increase varies to a great extent not only because of the annual weather conditions and the nature of the preceding crop, but also because of the amount of infected crop residues remaining on the soil surface, which depends on the soil tillage methods and the preceding crop.