Basal bark treatment of invasive trees is an approach designed to limit damage to non-target vegetation in the vicinity, but non-target injury is still documented. No study of basal bark treatments has examined the release of herbicide residues from roots of treated plants and resulting non-target impacts. Studies were conducted in Alaska interior and coastal boreal forests on basal bark treatments with aminopyralid and triclopyr on active-growth and dormant invasive chokecherry (Prunus padus L.). The study assessed non-target damage and soil herbicide residue using a combination of visual evaluations, bioassays, and soil residue analyses. Non-target damage from herbicide residues were identified in 40% of treatments containing aminopyralid with triclopyr, 60% of treatments containing aminopyralid alone, and 5% of treatments containing only triclopyr. Laboratory studies of aminopyralid treatments to saplings isolated the effects of herbicide exudation from roots, which was found to be significant, and the magnitude was dependent on dose. Herbicide soil residues in field and laboratory experiments were quantified with analytical detection and plant bioassays. Aminopyralid soil residues were identified in 57% of field treatments receiving 8 to 60 ml of herbicide solution (2% ai) and 70% of laboratory treatments receiving 10 µl of herbicide solution (2% to 16% ai). Triclopyr residues were found from one field treatment following dosage with 28 ml of herbicide solution (18.5% ai). Anatomically, plants grown in soils associated with herbicide-treated trees, both in the field and lab, grew less dry mass than non–herbicide treated controls. This study provides the first evidence that root exudation of herbicide following basal bark treatments contributes to non-target damage of adjacent vegetation and to accumulation of soil herbicide residues. This is an important new factor for integrated pest management within basal bark treatment systems and has implications for other herbicide application types such as injections and frill, as well as determining whether root exudation is species or herbicide specific.

Introduction. Plants developmechanisms that allow them to compartmentalize injuries that theysuffer during their life. In trees, pruning and injection treatmentsmust be used in accordance with precise rules to reduce risks resultingfrom the injuries created. Sealing in palms. Palms,contrary to widespread belief, are quite capable of “healing” injuries(sealing); because of an anatomy quite different from trees, thesealing process in palms is much simpler. Compartmentalizationof injection wounds. The controversy on the use of injectionin trees is due essentially to initial mistakes that have then beenrectified. Injection in palms against the red palm weevil.For palms, for decades, this technique has been employed withoutproblems and with great efficiency against various pests, including Rhynchophorus ferrugineus, the red palm weevil(RPW). Its use has been reserved for exceptional situations eitherto face abnormal pest proliferation, uncontrollable by other techniques,or to implement eradication programs. Integrated eradicationprogram. In such a program, the main aim of injection treatmentsis preventive. With long-persistence insecticides, the number of treatmentscould be greatly reduced. The resulting savings in time and moneywould enable the organization of the treatments of all the palms locatedin an infested area, and consequently the rapid eradication of thepest. New perspectives. We established that insecticidesapplied by injection were capable of protecting palms with onlytwo or even one treatment per year. These results suggest a radicalimprovement in programs to eradicate RPW, while considerably reducingthe risks to health and the environment compared with spray treatments.