EFFECT OF GLYPHOSATE-TREATED HENBIT (LAMIUM AMPLEXICAULE) AND DOWNY BROME (BROMUS-TECTORUM) ON FUSARIUM-SOLANI F SP. PISI AND PYTHIUM-ULTIMUM

Greenhouse studies were conducted to determine the following: if treat ing henbit or downy brome with glyphosate increased populations of Fus arium solani f. sp. pisi and Pythium ultimum in soil and rhizosphere s oil; if treating henbit or downy brome with glyphosate increased root colonization and infection by F. solani f. sp. pisi or P. ultimum; and , if henbit and downy brome are hosts of F. solani f. sp. pisi or P. u ltimum. Pythium ultimum populations increased only in soil containing glyphosate-treated henbit. Fusarium solani f. sp. pisi and P. ultimum populations increased in rhizosphere soil from glyphosate-treated henb it, while only P. ultimum populations increased in rhizosphere soil fr om glyphosate-treated downy brome. These results suggest that peas pla nted in soil where either downy brome or henbit had been treated with glyphosate could be exposed to higher populations of F. solani f. sp. pisi and P. ultimum. Root colonization and infection, plant height, an d root weight data indicated that henbit and downy brome are alternate hosts of P. ultimum. F. solani f. sp. pisi colonized, but did not rea dily infect roots of downy brome and henbit.