Do you have an evergreen native oak tree gracing your property or neighborhood? Lately, you might have noticed something odd – brown leaves amidst an otherwise healthy canopy, especially in the lower portion of the tree. If this caught your eye, take a closer look at the leaves or twigs to see if they match any of the following descriptions:
- The leaves are splotchy – one leaf might be green, yellowish, and brown all at once.
- The tip of an entire twig is brown – multiple leaves look completely dead.
- There are brown leaves, but they aren’t at the tips – rather, they are further back.
Splotchy Leaves: Two-horned oak gall wasp (Dryocosmus dubiosus)
If your leaf has a splotchy appearance, turn it over and check for tiny bumps along the veins on the underside. These bumps, known as galls, might have two distinct horns, hence the name “two-horned oak gall wasp.” A gall wasp is a wasp that lays eggs in plants, which triggers a growth (the “gall”) that surrounds the developing baby wasp. While these galls may look alarming, they do not cause any long-term damage. Despite potential leaf loss, rest assured the tree will bounce back as twigs and branches remain alive. During heavy infestations, natural predators usually emerge, so there’s often no need for intervention. For more information, check out this newsletter: https://www.traversotree.com/there-apples-tree/
The tip of an entire twig is brown: Twig blight (Cryptocline cinerescens)
If multiple leaves on a twig are completely brown, it could indicate twig blight – a common issue for oaks – caused by a fungus. As with most fungi, it favors moisture and tends to spread during rainy periods, affecting the tree’s tender new growth. Unless the tree is already compromised, patience is key as affected leaves will eventually shed. While fungicides may offer a solution, their effectiveness often depends on post-pruning application, which can be costly and limited to specimen trees. Focus on improving the growing conditions for sustained tree health.
Browning leaves farther back in the canopy of the tree: Normal leaf turnover
Deeper browning within the canopy may simply indicate regular leaf turnover. Although occurring earlier than expected, coast live oaks routinely shed older leaves in spring, a natural part of their life cycle.
It’s possible to encounter a combination of all these issues simultaneously. But again, none are a cause alarm, with your focus best directed towards providing optimal growing conditions.
If your tree presents different symptoms (like an entirely brown canopy) or recent weather events have you concerned, give us a call to schedule an appointment with one of our arborists.