Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 4, 2007
Publication Date: May 1, 2007
Citation: Henry, W.B., Shaner, D.L., West, M.S. 2007. Spectrophotometric assessment of glyphosate rainfastness with various surfactant levels on velvetleaf (Abutilon theophrasti) and soybean (Glycine max L.) [abstract]. Proceedings 2007 Weed Science Society of America Annual Meeting. p. 22. Technical Abstract: Glyphosate is one of the most commonly used herbicides in the world. A practical concern to farmers is how quickly following an herbicide application is the herbicide rainfast? To address this question, a rainfastness study was conducted at the Central Great Plains Research Station in Akron, CO in the summer of 2006. Greenhouse studies examined the response of glyphosate application at 105 g ae ha-1 to soybean and 210 g ae ha-1 to velvetleaf in 140 L ha-1 spray volume. Surfactant levels were 2%, 0.4%, 0.001% and none. The velvetleaf and soybean plants were in the 4 to 5-leaf and 2-leaf stage, respectively. Glyphosate application was determined with a spectrophotometric based leaf disc assay at 3 and 7 days after application. This assay uses 12, 4 mm leaf discs from the growing point of the plant to determine elevated shikimate values in the treated crops compared to the untreated controls. Substantial differences were observed among washoff treatments and among surfactant level treatments.