Impact of agronomic practices and environment on diseases of wheat and lentil in southeastern Saskatchewan

To determine the effect of tillage and rotation on plant diseases, their se verity and prevalence were monitored on spring wheat, lentil, and field pea grown in rotation with zero and conventional tillage at Indian Head, SK, f rom 1992 to 1995. Root disease severity of wheat was less under zero tillag e than conventional tillage, but leaf spot severity was unchanged. Incidenc e of the causal agents from roots was variable, such that Fusarium spp. wer e higher under zero tillage than conventional and Bipolaris sorokiniana was lower. Pyrenophora triticirepentis was the only foliar pathogen more preva lent under zero tillage than conventional. Rotation did not affect the path ogens causing root disease. However, the rotation of canaryseed-sunola-whea t-lentil had higher disease severity and levels of Septoria tritci on wheat compared with wheat-canola-wheat-lentil or wheat-pea-wheat-lentil. Neither crop rotation nor tillage practice had a measurable impact on lentil disea ses, but epidemics of Ascochyta lentis and Botrytis cinerea were most sever e in treatments with the densest plant stands. Multivariate analyses explor ed trends of tillage, rotation, and environment over years demonstrating th at regardless of tillage or crop rotation practices, the annual environment was the most important factor limiting the severity of disease and the pre valence of causal agents in the complex.