There are several signs that can indicate that a tree's leaves are diseased. One of the most common symptoms is leaf discolouration, which can range from pale blotches to deep brown or black spots. Another common sign of leaf disease is scorching, characterised by dry, brown patches along the edges of leaves. Curling, distortion, and premature drop are common symptoms of leaf disease. In some cases, a tree may produce an abundance of fruit or seed pods when its leaves are diseased. While these symptoms can be indicative of tree leaf disease, it is important to consult with a certified arborist to confirm a diagnosis.