Wasp Galls

If you have oak trees in your yard, you may have noticed weird growths on the leaves.  They are called galls and roughly 90% of oak galls are formed by parasitic wasps. They come in all kinds of shapes and sizes, each one specific to the species of wasp inside them.  Our pin oak tree has two different kinds on its leaves.  One looks like a tan puff-ball about 3/8 to 1/2 inch long.  Nothing really great to look at.  I’ve been tempted to cut one open to see the developing organism inside.
The other gall is a tiny red fuzzy ball ranging from 1/8 to 1/4 inch.  There are so many of these all over our tree.  From what I have read, I need not be concerned.  The galls do not harm the tree, and the wasps that emerge do not sting humans.

How do these galls form?  Evidently, the gall-making insect lays an egg on the leaf. The larva hatches and secretes powerful growth chemicals that interact with the tree’s growth hormones causing the over-development of plant tissue. The tissue rapidly grows around and encloses the larva.  The larva inside benefits by being somewhat protected from predators and gains nutrition from the tissue inside the gall.  In order for the gall to form successfully, this all must take place just as the new leaves are beginning to unfold in the spring.
The wasps that make galls are smaller than 1/8 of an inch and are not as well-described as the galls they make.  I do not know what species was responsible for this one.

Now, I do realize that these aren’t flowers, but they are colorful growths on this oak tree.  So I’m sharing them with my friends at Today’s Flowers.  Click on the badge below to view flower photos from all over the world.