Technical Report No. 7

EFFECTS OF APPLICATION OF GLYPHOSATE ON CORDGRASS, SPARTINA ALTERNIFLORA, AND ADJACENT NATIVE SALT MARSH VEGETATION IN PADILLA BAY, WASHINGTON

Douglas A. Bulthuis and Brady A. Scott

December 1993

Bibliographic Citation
Bulthuis, Douglas A. and Brady A. Scott. 1993. Effects of application of glyphosate on cordgrass, Spartina alterniflora, and adjacent native salt marsh vegetation in Padilla Bay, Washington. Washington State Department of Ecology, Padilla Bay National Estuarine Research Reserve Technical Report No. 7. Mount Vernon, Washington. 29 pp.

Abstract
The herbicide, glyphosate (Rodeo® with X-7® spreader), was applied with a backpack sprayer at a concentration of 2 quarts per acre on five experimental plots of Spartina alterniflora and adjacent native salt marsh vegetation in Padilla Bay Washington. Glyphosate was applied in July 1992 during a relatively low tide to maximize the time of exposure before inundation of the vegetation by high tide. Glyphosate had no effect on S. alterniflora, Salicornia virginica or Distichlis spicata in one, two or twelve months following application as measured by density, percent cover of live and dead plants or biomass of plants. Application of glyphosate did have an effect on Atriplex patula. A. patula had significantly lower percent cover and lower biomass in treatment plots than in control plots two months after application of glyphosate. It is suggested that the lack of any effect of glyphosate on S.alterniflora, S. virginica and D. spicata is due to the short time of exposure (about 8 hours) to the herbicide; and that the effect on A. patula is due to the location of A. patula at this site, higher in the intertidal, so that exposure to the herbicide was longer than for the other three species.