Fate of Glyphosate in Deciduous Fruit Trees

Abstract

Glyphosate [N-(phosphonomethyl)glycine] was applied to selected areas on young apple (Malus sylvestris L.), pear (Pyrus communis L.), sour cherry (Prunus cerasus L.), and peach [Prunus persica (L.) Patsch] trees to observe tree response. Injury occurred only on newly planted peach when contact was made on the basal 12.7 cm of tree trunks. Glyphosate effectively killed suckers without damaging trees. When sprays were applied to a lower branch of apple trees, local injury occurred the same season and the following year, but symptoms were not visible in other portions of the tree. Radiolabeled glyphosate was applied to the basal trunk, leaves, suckers, and fruit of 4-yr-old ‘MacSpur’/MM106 apple and 5-yr-old ‘Bartlett’/seedling pear. Applications on basal trunk areas produced no detectable radioactivity in leaves, buds, or fruits at harvest time. Applications on sucker leaves produced radioactivity only in the treated and adjacent sucker tissue and not in other portions of the tree. The 14 C-glyphosate moved readily from the treated leaves of lower branches to other leaves, buds, and developing fruit on the same branch but was not detectable in other areas of the tree. After 90 days, 92 to 98% of the extractable radioactivity in leaf, bud, or fruit tissue was unaltered 14 C-glyphosate.