SummarySaprophytic survival and pathogenicity of Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker were evaluated in sterile and unsterile Western Australian wheat field soil treated with the herbicides glyphosate, diquat + paraquat, or trifluralin. Survival in colonized straws and subsequent pathogenicity were not affected by the herbicide treatments in sterile soil. In unsterile soil, however, survival and pathogenicity were higher in glyphosate or diquat + paraquat‐treated than in untreated or trifluralin‐treated soil. Incorporation of untreated natural soil into fumigated soil, to give concentrations of 1 and 10% natural soil in the mix, reduced disease in comparison with that in 100% sterile or 100% natural soil. Disease in fumigated soil increased progressively with increasing concentrations of glyphosate‐treated, unsterile soil. Pre‐treatment of wheat plants or soil with glyphosate before exposure of the host to the fungal pathogen or to other soil micro‐organisms showed that the increase in disease following glyphosate treatment was not related to the direct effect of the herbicide on the host.