The answer to 'why is my tree brown patches' is that there are several common causes, including disease, pests, drought stress, or winter damage. The symptoms may include discolored, wilting, or dying leaves and branches. Addressing the underlying issue quickly is important to save the tree.
If the brown patches are limited, you may be able to treat the tree yourself with pruning, pest control, or adjusting watering. However, if the problem is widespread or you're unsure of the cause, it's best to call in a certified arborist or tree care professional to properly diagnose and treat the issue.