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 severity and prevalence were monitored on spring wheat, lentil, and field pea grown in rotation with zero and conventional tillage at Indian Head, SK, from 1992 to 1995. Root disease severity of wheat was less under zero tillage than conventional tillage, but leaf spot severity was unchanged. Incidence of the causal agents from roots was variable, such that Fusarium spp. were higher under zero tillage than conventional and Bipolaris sorokiniana was lower. Pyrenophora triticirepentis was the only foliar pathogen more prevalent under zero tillage than conventional. Rotation did not affect the pathogens causing root disease. However, the rotation of canaryseed-sunola-wheat-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 diseases, but epidemics of Ascochyta lentis and Botrytis cinerea were most severe in treatments with the densest plant stands. Multivariate analyses explored trends of tillage, rotation, and environment over years demonstrating that regardless of tillage or crop rotation practices, the annual environment was the most important factor limiting the severity of disease and the prevalence of causal agents in the complex.