Effects of Herbicide-Induced Stress on Root Colonization of Soybeans by Macrophomina phaseolina. C. H. Canaday, Former Postdoctoral Fellow, Departments of Agronomy and Plant Pathology, University of Missouri, Columbia 65211. D. G. Helsel, Assistant Dean, College of Agriculture, and T. D. Wyllie, Professor, Department of Plant Pathology, University of Missouri, Columbia 65211. Plant Dis. 70:863-866. Accepted for publication 13 February 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-863.

Effects of herbicide-induced stress on root colonization of soybeans by Macrophomina phaseolina varied with herbicide. In field studies, stresses induced with chloramben and 2,4-DB significantly increased root colonization by M. phaseolina, whereas herbicide stress induced with alachlor significantly reduced root colonization by M. phaseolina. Herbicide stresses induced with glyphosate and vernolate had no effect on root colonization by M. phaseolina. Trifluralin significantly reduced root colonization by M. phaseolina in the absence of significant herbicide stress. With the exception of trifluralin, changes in root colonization by M. phaseolina appeared more closely related to root injury than to herbicide stress per se.

Keyword(s): acifluorfen, bentazon, Glycine max.