Posted May 25, 2017 09:05h in Pests & Diseases 5 Comments
Some of the newly installed oaks on campus appear to have grown cotton balls with pink spots. These are actually a type of tree gall called Wool-sower gall.
This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). These wasps lay their eggs on a specific plant and the eggs produce the grubs whose secretions cause the gall formation. The gall provides protection and nutrition. Their favorite host plants are oaks.
The galls do not harm the tree, so the best integrated pest management practice is to co-exist. One-to three-weeks later a wasp will emerge. It is another amazing insect-plant relationship.
WendyPosted at 10:09h, 25 May
Have never seen these before, very interesting, Have to keep our pollinators reproducing! I am really enjoying these posts, so informative, and the plants are beautiful!
Becky RobertPosted at 08:25h, 30 May
Thank you Wendy. There are some really interesting insects out there! I am always amazed how much we still don’t know about the natural world. For instance, I could find little to no info of the adult habits of this creature.
Rose MartinPosted at 08:46h, 07 June
I just found a few oak trees that have the wool sower gall. What do I do with them. Do I just leave them be?
Lars RasmussenPosted at 11:56h, 09 June
Hi Rose. I would just leave them be. Unless they are all over the trees in high numbers it should not be a problem. They may have hatched out by now.
Plant Health Coordinator
Nancy ArmstrongPosted at 10:41h, 29 May
Just discovered a Wool Sower gall on a small oak sapling. I was wondering why the gall is sticky? Also, exactly how does the wasp create such an intricate structure ?