PRE-HARVEST RETTING OF FLAX WITH GLYPHOSATE - EFFECTS OF NOVEL METHODS OF SPRAY APPLICATION ON PENETRATION OF THE CANOPY AND UNIFORMITY OF DEPOSITION

Four methods of spray application were compared in 1986 with the recommended method of glyphosate application for pre‐harvest retting of flax (Linum usitatissimum). Sampling individual plants immediately after application of glyphosate and dye demonstrated that spray penetration through the crop canopy, measured as dye deposition on the lower stem as a percentage of total deposition per plant, was the same for all methods of application. None of the methods of application improved the uniformity of dye deposition. The following year, effects of deseeding prior to spraying and of using an air‐assisted sprayer were investigated. Deseeding increased dye deposition on the lower stem but did not improve the efficacy of glyphosate. Application with an air‐assisted sprayer increased the proportion of spray deposited on the lower stem but not the absolute amount deposited or the efficacy of glyphosate. Dye deposition on individual plants varied greatly for all methods of application and, when glyphosate was applied using the same methods, undesiccated plants occurred in all plots. Considerable improvements in spray penetration and uniformity of spray deposition appear necessary for successful pre‐harvest retting of flax with glyphosate. Copyright © 1990, Wiley Blackwell. All rights reserved