Brown balls on trees are actually the result of the activity of certain wasps that use trees as hosts for their developing larvae.Brown Balls on Trees

These balls are a common sight throughout North America, Europe, and Asia. Let’s take a dive into understanding what they are and how you can manage them.

Why Are There Brown Balls in Your Trees?

There are brown balls in your trees because of wasps or fungus. Galls can be confused with oak tree fungus balls, which are caused by lumps of fungal mycelia that grow on dead or decaying matter. These fungus balls are often round or irregularly shaped and are small to large.

On the other hand, brown oak galls, also known as oak apple galls, start out when female wasps lay their eggs on the twigs or leaves of the oak tree. As the eggs hatch and the larvae begin to feed on the tree’s tissues, they secrete chemicals that trigger the formation of a gall.

However, insects are not the only ones to blame. Fungi and bacteria can sometimes contribute to the formation of brownish balls or growths on trees. Fungal infections, such as Hypoxylon canker, can result in brownish-black fruiting bodies and are different from the aforementioned fungus balls.

Fungal infections sometimes appear as brownish balls on trees or leaves through the development of galls. Galls are abnormal growths triggered by specific fungi, providing a protective environment for fungal reproduction. The brown coloration is a result of pigmentation changes or the accumulation of fungal spores or substances within the gall.Causes of Brown Balls on Trees

Bacterial infections, like bacterial canker caused by Pseudomonas syringae, can lead to raised, brownish lesions. Other factors like physiological disorders or environmental stress can also contribute to the formation of brownish balls. Despite these unusual circumstances, most of the time, these balls are attributed to insects and their larvae.

– Effects of Galls on Trees

Despite its unusual appearance, the oak gall is generally harmless to oak trees. While heavily infested trees may experience reduced growth or yield, most trees can tolerate a moderate number of galls without suffering any significant damage. In fact, some species of oak have evolved to form galls as a defense mechanism against insect herbivores, including wasps.

– Types of Galls

In addition to brown oak galls, there are many other types of galls that can form on oak trees, including bullet galls, horned galls, and silk button galls. Each type of gall is formed by a different species of wasp and has a unique shape, size, and texture.

There are several wasps that are known to cause galls. One of the most common is the Cynipidae family of wasps, which includes species, such as the oak apple gall wasp Amphibolips confluenta. The other two are the wool sower gall wasp Callirhytis seminator and the horned oak gall wasp Callirhytis cornigera.

These wasps lay their eggs in the buds or leaves of the oak tree, which causes the tree to produce the abnormal growth that forms the gall. Other types of wasps, such as the gall-making sawflies under the family Tenthredinidae may also be involved in forming galls.

While galls are most commonly linked with wasps, they can also be caused by other insects, such as mites, aphids, and flies. There are even some gall-forming insects that are highly specialized, and may only target specific species or parts of the tree.

– Relevance of Galls on Trees

Galls can vary in their impact on the host, and it all boils down to the type of gall and the severity of the infestation. In some cases, galls may cause significant damage to the tree, reducing growth and yield or making the plant more susceptible to other pests and diseases. In other cases, galls may have no noticeable effect on the tree’s health or growth.

Despite their potential to cause damage, galls are also important components of many ecosystems. They can provide habitat and food for various insects and other organisms, and may even be used as a food source by humans in some cultures.

How Do You Manage the Brown Round Balls in Your Tree?

There are several options for managing galls on trees. It’s worth noting though that in most cases, the galls do not pose a serious threat to the health of the tree and may not require treatment. However, it is important to first diagnose the problem before diving in with solutions.Remedies for Brown Balls on Trees

– Prune Affected Tree Parts

One common approach to managing galls is to prune affected branches or twigs. This can help to reduce the overall number of galls on the tree and minimize the risk of falling debris. It’s important to prune in the dormant season, as pruning during the growing season can encourage new growth and potentially create more sites for wasp infestation.

– Apply Insecticides

This option can help to kill the adult gall wasps before they have a chance to lay their eggs and form new galls. However, it’s important to note that insecticidal sprays can also harm beneficial insects, so this should only be done as a last resort and with caution.Applying Insecticides on Trees

If you are considering insecticides, then you need to first figure out which insect is causing the condition. Identifying the insect species responsible for a particular type of gall can be challenging, as there are many different types of insects that are capable of causing galls on plants.

Different species of insects tend to produce galls that have characteristic shapes, sizes, colors, and textures. For example, oak apple galls tend to be large, round, and woody, while bullet galls are small and bullet-shaped. Examining the physical characteristics of the gall can provide clues as to which type of insect may be responsible.

Various insect species tend to produce galls at different times of the year and on different parts of the tree. For example, some gall-forming wasps lay their eggs on oak leaves in the spring, while others lay their eggs on the stems or roots in the fall. By observing the timing and location of the gall, it may be possible to narrow down the possible suspects.

– Maintain Tree Health

Preventing galls can be challenging since they are caused by the activity of certain species of wasps and are a natural part of the tree’s ecosystem. One important step is to maintain the overall health of the tree.

This can be done by ensuring that the tree is properly watered, fertilized, and pruned as needed. A healthy tree is better able to withstand insect infestations and is less likely to be heavily impacted by these galls.

– Minimize Tree Damage

Another key factor in preventing galls is to minimize damage to the tree. This can be done by avoiding unnecessary pruning, protecting the tree from damage, and taking steps to reduce stress on the tree. Stressed trees are more vulnerable to insect infestations, so it’s important to avoid over-watering, over-fertilizing, and other practices that can stress the tree.

– Grow More Resilient Varieties

In some cases, homeowners and gardeners may choose to grow oak species that are less susceptible to galls. While no species is completely immune to infestation, some types of oak are less attractive to the wasps that cause galls.

– Consider Natural Tree Adaptation and Evolution

It’s also important to note that some species of oak have evolved to form galls as a natural defense mechanism against insect herbivores. Removing the galls may actually be detrimental to the health of the tree, which is something to think about.Solving Brown Balls on Trees

Frequently Asked Question

– How Long Does a Brown Oak Gall Typically Remain on the Tree?

A brown oak gall typically remains on the tree until they are mature, at which point they will fall to the ground or be dislodged by wind or rain. The lifespan of a brown oak gall can vary depending on the species of wasp involved and the environmental conditions.


Now that you know what those round balls on trees are, you can rest easier knowing that they’re pretty much harmless to the tree. To recap, here are what we’ve covered about oak tree galls on branches:

  • While there are many different types of insects that cause galls to form, the most prevalent ones are made by wasps.
  • Manage these galls by pruning the affected parts, applying insecticides, and maintaining tree health.
  • You can also minimize tree damage, grow more resilient varieties, or consider the galls as part of the tree’s health gauge.

Simply keep all the information you’ve gleaned from this article if and when you see anything resembling galls in your trees so you’ll be prepared to take the proper steps!

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