The answer to 'tree disease' is that there are several common causes of tree diseases, including fungal infections, bacterial infections, and insect infestations. Symptoms can include discolored or wilting leaves, dead or dying branches, and overall decline in the tree's health. Solutions can vary depending on the specific issue, but may involve pruning, treating with fungicides or pesticides, or in severe cases, removing and replacing the tree.
In many cases, it's best to call in a professional arborist or tree care specialist to diagnose and treat the problem. They have the expertise and equipment to properly identify the issue and apply the right treatment. However, for minor problems or preventative maintenance, some homeowners may be able to address the issue themselves with the right information and precautions.