It depends on where the imprelis MAY still be "residing". By that I mean if it is in ONLY the affected terminals and has not causing establish growth to brown, then pruning off those terminals will/should remove the herbicide with it. Imprelis breaks the gibberillic chain, thats how it controls weeds, by inhibiting growth. However it did the same thing in shallow-rooted conifers. Since younger trees move most of their water to new growth, only new growth was affected, older trees tend to equally disperse their water as new growth is not the priority, hence many mature trees were killed as ALL growth was affected. It also depends on overall health PRIOR to the application, as well as soil conditions (i.e. the more compacted the soil the longer imprelis lasts). Also organic matter in the soil is imporant as the primary mode of degradation is microbial. Also let people know NOT to fertilize these trees, NPK (urea-based) fertilizer can lower soil PH, which keeps the imprelis "active" longer. This product was designed to be applied ONCE, for season-long control, therefore soil life can be between 90-120 days. Now that would mean its no longer EFFECTIVE after that time. It does NOT mean its GONE after that time. Herbicide degradation is measured like uranium in "half-life" and this stuff's is LONG...