INHIBITION OF DRECHSLERA-TERES SCLEROTIOID FORMATION IN BARLEY STRAW BY APPLICATION OF GLYPHOSATE OR PARAQUAT

Field-grown barley straw was inoculated with Drechslera teres f. sp. t eres or D. t. maculata, treated with two herbicides used in no-tillage barley production, and then incubated in controlled conditions to ind uce sclerotioid structure morphogenesis (resting form). Formulated her bicides containing glyphosate or paraquat were applied at three differ ent concentrations. Applied at the recommended field rate, these herbi cides significantly reduced sclerotioid structure production by D. ter es. In addition, their morphology and myceliogenesis were modified in the presence of both herbicides at the recommended field rate. Glyphos ate 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 de pending on the herbicide, concentration of the active ingredient, meth od of application, and forma specialis of the pathogen.