Inhibition of Drechslera teres Sclerotioid Formation in Barley Straw by Application of Glyphosate or Paraquat. H. TOUBIA-RAHME, Laboratoire d'Ingenierie Agronomique, Ecole Nationale Superieure Agronomique de Toulouse, 145, Avenue de Muret, 31076 Toulouse Cedex, France. D.-E. ALI-HAIMOUD, G. BARRAULT, and L. ALBERTINI, Laboratoire d'Ingenierie Agronomique, Ecole Nationale Superieure Agronomique de Toulouse, 145, Avenue de Muret, 31076 Toulouse Cedex, France. Plant Dis. 79:595-598. Accepted for publication 28 May 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0595.

Field-grown barley straw was inoculated with Drechslera teres f. sp. teres or D. t. maculata, treated with two herbicides used in no-tillage barley production, and then incubated in controlled conditions to induce sclerotioid structure morphogenesis (resting form). Formulated herbicides containing glyphosate or paraquat were applied at three different concentrations. Applied at the recommended field rate, these herbicides significantly reduced sclerotioid structure production by D. teres. In addition, their morphology and myceliogenesis were modified in the presence of both herbicides at the recommended field rate. Glyphosate was more inhibitory than paraquat; no sclerotioid structures were produced in straw when glyphosate was applied before colonization by D. teres. The effect of the herbicides at 10-8 and 10-4 M varied depending on the herbicide, concentration of the active ingredient, method of application, and forma specialis of the pathogen

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