INFLUENCE OF CROP SUCCESSION ON FOOT AND ROOT DISEASES OF WHEAT

The consequences of different crop successions on foot and root diseases were analysed on a subsequent winter wheat crop managed identically, regardless of crop succession. At flowering, tillers and roots were assessed for eyespot (Pseudocercosporella herpotrichoides), take-all (Gaeumannomyces graminis var tritici) and sharp eyespot (Rhizoctonia cerealis). As a consequence, we can propose a simple model of the effect of the preceding crop and the I before that on the 3 diseases. This model is based on a crop classification into 3 groups: host, amplifying crop and non-host for take-all and sharp eyespot; and 'strong/weak' host, amplifying crop and non-host for eyespot. Whereas host crops tend to increase and non-host crops to decrease disease risk, amplifying crops (maize, ryegrass, etc) can only increase risk if they are associated with host crops.