Glyphosate (Roundup) Toxicity to Niagara Grapevines

Abstract

One-year-old Niagara grapevines (Vitis labruscana Bailey) were trained to single shoots and schematically divided into four sections (tip to base). Leaves of one of the four sections (A = apical; SA = subapical; P = penultimate; and B = basal leaves) from each shoot were dipped into a solution containing 8.93 g, a.e./liter glyphosate. Vines of treatment A reacted as though they had been physically shoot tipped; terminal growth ceased and vigorous lateral growth developed. In treatment SA treated leaves plus most of those located above the treated portion developed glyphosate symptoms. Leaves on lateral shoots were also abnormal. No lateral shoots developed in treatments P and B. Root growth was most severely reduced in treatment P. Terminal shoot growth was severely reduced on all treated vines. Both top and root growth of dormant cuttings following rest were reduced in treatments SA, P, and B.