Woolly Oak Leaf Galls

Strong winds have blown for days. They’ve blown fuzzy “balls” in our driveway from the huge oak across the highway.

These are actually woolly oak leaf galls that are formed by gall wasps. They originally formed in a tight mass of 4-6 galls on the underside of the midvein of the leaf. There’s a hard structure in the middle of each that feels like a seed.

Somehow the wool was worn off part of this gall.

I found this when I removed the wool. It measured 1/4 inch wide at the bottom and 3/16’s tall.

I took this picture through my stereo microscope. Obviously, the grub wasn’t big enough to see yet. All wasp galls typically have an outer wall, a spongy fiber layer and a hard seed-like structure where the grub develops.

My artistic mind had problems understanding technical information about things like how the galls form. Gall wasps emerge during the winter and lay eggs in the spring. This species lays on the underside of the midvein or sometimes the lateral ones. After they hatch, the grubs salvia secretions act as a plant growth regulator and force the leaf to form the gall.

I just don’t see how the grub’s salvia could cause this. How does the wool form outside the gall? What is its purpose?  It’s just so amazing and definitely something to wonder about.


8 responses to this post.

  1. Very interesting.


  2. Too cool and great pics..:-)


  3. Definitely amazing!


  4. Posted by my secret love for you on December 3, 2012 at 9:22 am

    this is all very informative to me, thanks great posts!


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