Friday, November 11, 2011

Goldenrod and the Three Galls - Blisters, Bunches, and Balls

Who can pass up a goldenrod patch thick with galls?
Those round, cherry-sized stem galls are the familiar Goldenrod Ball Galls.
Goldenrod Ball Galls
 These galls are caused by the Goldenrod Gall Fly, Eurosta solidaginis.
   The gall fly larva can modify the plant's growth.  It causes the plant to grow this specialized structure where it lives and feeds and even overwinters.
Here is a picture of a Goldenrod Gall Fly larva snug in its home/pantry.
   Notably, the larva excavates an escape tunnel (see a picture of the larva's escape tunnel here) to just below the gall's exterior skin. The larva does this in the fall, then overwinters in the center of the gall.  During the winter it survives multiple freeze/thaw events.  In the spring the larva pupates.  When the young goldenrod plants are growing the gall fly hatches, crawls up its tunnel, inflates its face balloon (ptilinum - see a few pictures here, or here), pops open its escape hatch, and enters the goldenrod patch to find a mate in order to ensure the process is repeated.
Goldenrod Gall Fly -  Eurosta solidaginis
    However, there's a good chance a parasitic wasp may emerge from a gall in the spring instead of the gall fly since many of the galls are parasitized.  Also, Chickadees and woodpeckers are often seen (and heard) extracting the gall's inhabitants.
Ball galls can vary in size.  

Some stem galls are not round but elliptical spindle-shaped, these are caused by moth caterpillars. 
   There are several species that cause these galls like Epiblema spp. and Gnorimoschema gallaesolidaginis.  I believe the latter species was the maker of the gall pictured below.  The photo below shows the cross section of a gall of the Goldenrod Elliptical Gall Moth and its empty pupal case.
Besides those two stem galls, there are other kinds of galls in the goldenrod patch.
I'll change my focus from the stem galls to the bunch galls.

In the photo below there are "bunches" of bunch galls.  These leafy clumps on the mains stem are home to goldenrod bunch gall midges.
Goldenrod bunch galls
You might say, "It can get a bit hairy out in the patch" as the goldenrod tries to circumvent the interrupted growth of its main stem.
Amazingly, the galled plants are often able to produce seed.
   There are various species which cause these goldenrod bunch galls.  One of them is Rhopalomyia solidaginis.  Those gall midges are responsible for many of the bunch galls pictured above.

Another kind of goldenrod bunch gall is pictured below.
I cut open a couple of these bunch galls last year.  Unfortunately, I didn't look close enough to see exactly what I found.
Here is one of those bunch galls with an empty pupal case.
  Many other insects are found in the bunch galls alongside the gallmakers or their parasites. These fellow campers, or, "inquilines" make themselves right at home in the leafy galls.                                                

The picture below of  "Goldierod and the Three Galls" illustrates the the three gall types I've mentioned.
Actually, there are more galls in the patch besides the these three gall varieties.

At the risk of being galling, here are a couple more examples of galls associated with goldenrod.
These minute galls look like green seeds among the goldenrod's flowers..
 I believe they are Beaked Flower Galls caused by Schizomyia racemicola.  I found them growing in the little goldenrod patch in our fencerow. 
 An orange larva is visible through the hole.

Here is a picture of the little guy through the hand lens.

For me, one of the most fascinating goldenrod galls is the Black Blister Gall caused by a gall midge - Asteromyia carbonifera.
In the photo below, I have broken open one of the galls to expose the midge larva and its black symbiotic fungus.
Just think...the midge lays an egg and also infects the leaf with its fungus....
Ah, but this is just a sneak peek. 
A quick stroll through the patch. 
With all the gall makers, the inquilines, and the parasites, the goldenrod patch is an ecological goldmine
What a great place to be galling!


  1. What a wonderful way to start my day, Dana, walking through the goldenrod patch.

    I'll be looking more closely, when I take my dogs to the field up the street.

    Love the post title !

  2. Excellent article and photos! I have been meaning to look this up for years and now you've answered all my questions right here! Thanks!

    1. Carol,
      I'm pleased you found my site and have enjoyed the information and photos of goldenrod galls. Is there anything else you've "been meaning to look up for years"? Perhaps I've run across the same thing around here and could post some photos, etc.