This document discusses tree defects, decay, and D49. It defines defects as naturally occurring growth patterns that negatively impact a tree's stability or strength. Included bark, circling-girdling roots, and poor canopy structure are provided as examples of defects. Circling-girdling roots are caused by roots growing into an impenetrable surface. Decay is defined as the breakdown of woody material caused by injury, disease, or fungi. Decay can be prevented through proper pruning and planting practices. Various indicators of decay are given as reasons for tree removal or close monitoring. D49 is also mentioned but not described.