Maple leaf with red bumps and black spots

Asked June 6, 2018, 11:38 AM EDT

Hello, the leaves on my maple tree has red bumps and black spots. I’m wondering if this is of concern or if I should do something about it?

Washtenaw County Michigan

1 Response

The red bumps are galls, an abnormal growth of leaf tissue that occurs in response to egg laying of tiny insects. This does not harm the tree and many of the insects that cause galls are beneficial insects. No control needed. The browning spots are caused by a fungus, anthracnose which was brought on by the unusual extended periods of rain in May. Fungicides at this time would not change anything and are not recommended. This disease rarely causes much leaf fall and most leaves continue to function. As the season becomes hotter and drier there is less opportunity for the disease to spread. The following article does detail control measures in specific instances: