Question
Red Maple Leaf Spottin
I live in Tucson, Az. and have had this Acer palmatum for 15 months. In February I repotted it with 75% Miracle Gro Moisture Control Potting Soil and 25% Cactus Soil. It went from a thin 12" high stick with hardly any leaves to a thriving 18" miniature tree. Now I noticed these spots on several of the leaves. I have watered it every 3 to 4 days as needed since the leaves started sprouting shortly after repotting it. Could you please tell me what this is? This tree was a gift and I try to take good care of it even though I don't know too much about Maples.
AnswerThese are leaf spot caused by a fungus. I am going to guess it is Phyllostict leaf spot. A leaf spot that infects late in the growing season causes very little damage except maybe the leaves will fall earlier than normal. If you want to control the fungus the leaf surface would need to be sprayed with a fungicide in the spring. A large tree would be difficult to spray and in my opinion not worth the effort since the damage to the health of the tree is slight.
Phyllosticta Leaf Spot of Maple. Pathogen: Phyllosticta minima
Like many fungal leaf spots, this disease affects a number of maple species, most prominently Amur, Japanese, red and silver maple. The disease causes little damage because the infection is localized. Spots are roughly circular and develop into tannish spots with purple to red borders. Later in the season the spots often contain black fruiting bodies of the fungus arranged in rings inside the lesion. Although this disease is quite noticeable in the landscape, especially on silver and red maples, and causes concern among homeowners, damage is minimal and fungicides are rarely necessary. If fungicides are required use a labeled product containing mancozeb or chlorothalonil.
Most fungicides are sprayed early in the spring to prevent leaf spots. You could try a fungicide it should keep the spots from spreading but will not make the ones that are there go away. Check with your local nursery for a fungicide for leaf spots on trees.
