EFFECT OF CERTAIN HERBICIDES ON SAPROPHYTIC SURVIVAL AND BIOLOGICAL SUPPRESSION OF THE TAKE-ALL FUNGUS

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Summary

Saprophytic 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.

Ancillary

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