What Is Causing The Bumps On My Tree?

Have you been noticing abnormal growths on the trunk and branches of your trees? They could be galls, which are simply abnormal growths that occur on leaves, twigs, or branches. Identifying which type, however could pose a difficulty to someone who is not a certified Arborist as there are over 1500 different gall producers. Not all of these are cause by disease, however most of them are cause by insects and mites. The actual gall itself is produced by the tree in response to the egg-laying of mites and other insects on the tree. As the insects lay these eggs, they begin the process of plant growth hormones that produce abnormal cell growth, hence the galls.

Just as a fungus, galls come in all different shapes, sizes and colors. These large growths can be disturbing to look at, however usually do not pose a threat on the tree. However, there are a few different diseases that are very harmful and could potentially kill the tree, such as black knot galls and Fusiform rust galls.

Types of Unharmful Galls

Leaf Galls - You may have noticed irregular bumps on a leaf and thought they were carrying insect larvae, as it appears. In fact, by the time you have noticed these bumps these insects have moved on. They are just the result of the feeding of insects or mites, spiking this bumpy response from the leaf. As these protrusions aren’t pretty and might look harmful it is best to just let them be. If you notice them year after year this might signal a spraying is needed to keep the insects away.

Oak Galls - There are a number of different types of oak galls including:

  • Oak Apple Galls

  • Oak Bullet Galls

  • Wooly Oak Leaf Gall

  • Horned Oak Galls

  • Jumping Oak Galls

All of these are different sizes, shapes and colors and can be caused by different hosts. The good news is none of these will seriously infect your well established trees. If the trees are heavily infected by these galls, the most damage you might notice is some leaf drop or stem deformities.

Types of Harmful Galls

Black Knot Galls - primarily only infect plum and cherry trees but can also affect other fruit trees such as apricots and peaches. Black knot can be managed by a certified Arborist with some heavy pruning and disposal of the fungus it self but does not guarantee its survival.


Fusiform Rust - This specific disease is usually exclusive to Loblolly and slash pine trees but Oak trees are the alternate host. It has spindle shaped lumps and produces orange spores in the spring and is spread by the wind in March & April. Willow, laurel, and water oaks are especially at risk at this time because they are producing new leaves that the wind blown spores are drawn to. This fungus will not kill the tree immediately, in fact, the fungus can continue to grow for many many years beforehand.



If you have noticed any of these symptoms on your trees in Watkinsville, it is best to contact a Certified Arborist for a free assessment and disease diagnostic. These are typically free and could potentially save your beloved tree. At North American Tree Service we typically recommend heavy pruning of the area, if possible followed by a spray regiment to keep the tree healthy. Call us today for a free estimate!

(770) 554-9406

North American Tree Service