| This paper discusses three research studies, each investigating a different treatment window for controlling tree-of-heaven using effective and environmentally sound herbicide applications. In the first study, efficacy of the herbicides triclopyr and imazapyr was tested using injection and basal bark treatment methods. In the second study, efficacy of triclopyr with different levels of imazapyr was tested using the basal bark treatment method. In the third study, weekly timing of chemical controls was investigated. Our study yielded a recommendation to treat tree-of-heaven with a low volume basal spray of Garlon 4 in a non-aromatic penetrating oil when growth is maximized in early summer (June 1-July 12), following a period of at least average precipitation. Treatments with imazapyr damaged untreated neighbor stems, probably through root connections and/or root leaking, so use of this chemical is not recommended near high value timber trees. |
