Mower/weed wacker damage at the base of a tree (David Robinson, University of Illinois, Bugwood.org)
Mechanical damage to plants includes any activity that damages the roots, root collar, stem, branches or leaves. Damage to the roots, root collar or stem can manifest as crown dieback and leaf dieback. Mechanical damage is frequently caused by mowers/weed wackers/lawn maintenance tools, vehicles, soil compaction, soil piled on root zones or against a tree, over-mulching, girdling, construction, trenching in the root zone, vandals, improper planting, improper pruning and improperly aimed sprinkler heads.
Minimize mechanical damage by setting up tree protection zones to keep lawn maintenance equipment, vehicles, construction activities, etc., away from the tree and the root zone.