Tordon Herbicide: Not For Backyards
Tomato plant with distorted foliage caused by picloram.
Over the past few months, the Utah Plant Pest Diagnostic Lab received a few inquiries of distorted perennials, vegetables, and dying trees, all linked to the use of an herbicide called Tordon. Tordon (picloram; Dow AgroSciences) is used for controlling unwanted weeds and woody plants, and for treating cut stumps in forests and non-cropland areas. It is a “restricted use” product, meaning that it can only be applied by a licenced pesticide applicator. The use of Tordon in backyard settings to kill tree stumps or weeds, even by a licensed applicator, is prohibited by law and could result in civil fines by the Utah Department of Agriculture and Food.
The Tordon label states that trees growing near treated areas can occasionally be affected when their roots come into contact with and absorb herbicide residues from the soil or from roots of nearby treated trees. Therefore, Tordon should never be used near the root zone of desirable trees.
Dr. Ralph Whitesides, Professor and Extension Weed Specialist at Utah State University, says that this statement applies to the treatment of cut stumps as well. Tordon is persistent in the soil for a long time and broadleaf crops can be severely damaged even if the product was applied a year or two prior. Glyphosate, the active ingredient in Roundup and many generic herbicide formulations, should be used instead to kill stumps and to prevent sprouting from roots.
-Claudia Nizchwitz, Plant Pathologist