Weed Technology (2022) 36, 457-461

Drew J. Lyon and Mark E. Thorne (2022)
Smooth scouringrush (Equisetum laevigatum) control with glyphosate in eastern Washington
Weed Technology 36 (4), 457-461
Abstract: Smooth scouringrush has invaded no-till production fields across the US Pacific Northwest. The ability of Equisetum species to take up and accumulate silica on the epidermis and in cell walls may affect herbicide uptake. The objectives of this study were to measure the silica concentration in smooth scouringrush stems over time, and to determine how time of application affects the efficacy of glyphosate for smooth scouringrush control, with and without the addition of an organosilicone surfactant (OSS). Field studies were conducted at three sites in eastern Washington from 2019 to 2021. Three herbicide treatments (no herbicide, glyphosate, and glyphosate + OSS) were applied at four application times (May, June, July, and August) in 2019 fallow. The silica content of smooth scouringrush stems increased over the course of the 2019 growing season at all three sites. In 2020, smooth scouringrush stem densities were reduced when the 2019 herbicide treatments were applied in late June (12% of no herbicide density) compared to late July (24%) or August (30%). Smooth scouringrush stem densities at all three sites, in both 2020 and 2021, were reduced in the glyphosate + OSS treatment compared to glyphosate alone. In 2021, 2 yr after herbicide application, there was no effect of application timing for the glyphosate treatment without OSS, but stem densities were reduced when glyphosate + OSS was applied in late June (1%) compared with applications in late July (26%) or late August (21%). It is not clear if the cause of reduced glyphosate efficacy with late July and late August applications is the result of increased silica content in smooth scouringrush stems over time. Maximum glyphosate efficacy on smooth scouringrush was achieved with an application in late June and with the addition of an OSS. Control of smooth scouringrush with glyphosate + OSS can be sustained for at least 2 yr after application.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Drew Lyon

Research topic(s) for pests/diseases/weeds:
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Equisetum laevigatum (weed)		U.S.A. (NW)