Fungal leaf spot diseases are one of the most common group of plant diseases. Symptoms vary depending on the pathogen and host. Some common symptoms include frogeye or bull's eye spot, marked with conspicuous concentric rings; irregular, round, tan spots with small black dots (fungal fruiting bodies); angular tan or black spots; black or tan spots surrounded by yellow leaf tissue; oval-shaped leaf spots; raised leaf blisters; and tan to gray spots with red or purple margins. Fungal leaf spot diseases are favored by wet seasons, high humidity, and frequent overhead irrigation. Most leaf spots do not warrant special control measures. However, if the disease you are dealing with occurs annually such as black spot on rose or entomosporium leaf spot of photinia, consider using a fungicide on the plant's foliage. Contact your local Cooperative Extension office for specific information on pesticides.
Other control measures include raking and composting fallen leaves; using drip irrigation; purchasing only disease-free plants showing no signs of leaf spots; growing resistant varieties when available; choosing an alternative planting site. Most established shade trees can tolerate leaf spot diseases without significant damage.
