The Downside Of Magestic Oak Trees Are Gall-Forming Wasps!

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The Downside Of Magestic Oak Trees Are Gall-Forming Wasps!

13 December 2022
 Categories: , Blog

Oak trees are a majestic tree species that produces exceptional hardwood lumber when they reach the end of their lifespan. However, they are not without issues. One of the biggest is they act as hosts for many gall-forming wasp species.

If you've never heard of gall wasps, then here's what you need to know:

Species of Gall-Forming Wasps 

While many people think of wasps as one insect, there are various species. The main wasp species that form galls on oak trees include the following: 

  • Horned oak galls
  • Gouty oak galls
  • Leaf galls

Leaf galls are not harmful to oak trees. However, all gall hatch wasps which are stinging pests for people and pets. In contrast, horned and gouty oak galls form on branches and will kill a tree when the infestation gets bad enough. And these so-called "branch galls" or "twig galls" also hatch wasps that will harass you and your family.

Branch Galls

Various species of adult-branch oak gall wasps inject their eggs into the twigs and branches of oak trees. This injection causes the oak trees to grow special protective shells around each egg. The eggs hatch into larvae, injecting chemicals into the tree that form round galls for the wasp larva to feed on until they are ready to hatch. 

Since galls encourage the growth of unhealthy tree tissue, an infestation will severely damage the tree. In the short term, branches can become too weighty and break. Over time, a large branch gall infestation will kill an oak tree.

Horned Oak Branch Galls

Horned oak galls are branch galls with distinctive little pointy spines sticking out. Since they are the only galls with these spike formations, identifying horned oak galls is easy and straightforward.

Gouty Oak Branch Galls

Gouty oak galls look almost identical to horned oak galls but do not have spikey horns. If the galls you find on a branch of your oak tree are smooth, then they are likely gouty oak galls.

Leaf Galls

In contrast to branch galls, leaf galls form on the leaves of a tree. However, the rest of the process is the same. The leaf gall wasp species lay their eggs on the tree's leaves. When the larvae hatch, they inject chemicals to form galls on the leaves to feed on. 

Lastly, leaf galls will not kill your oak trees but can cause premature leaf drop and negatively affect photosynthesis.