Monday, April 26, 2010

Wool-sower Gall

Spring is a great time for gall watching.  As the leaves and buds are coming out, it is easy to spot plant galls which are frequently at their most colorful.  I will be posting a few galls over the next weeks.

The wool sower gall is an excellent example with a complex life cycle.  The gall to your right is the size of your finger tip and looks like a cotton ball with distinctive pink spots.  Like many tree galls, this is produced by a Cynipid (sin-a-pid) gall wasp.  These wasps are from 1-8 mm in length and many have a distinct hump on the back.  They lay their eggs on a specific plant and the eggs produce the grubs whose secretions cause the gall formation.  The gall in turn provides both protection and nutrition.  How it does it remains a mystery.  The most common host plants for the Cynipids are oak trees.  see Wikipedia on Gall Wasps
The Wool-sower gall is also called an Oak Seed gall, due to the seed-like appearance of the early larva inside the gall.  The gall is produced by the secretions of the grubs of a tiny gall wasp, Callirhytis seminator.  "These wasps invariably have alternation of generations in which one generation develops in one type of gall (leaf gall) and their offspring develop into another type of gall (stem gall). Wasps of each alternate generation are slightly different in size, resembling their grandparents more than their parents.  The galls of each generation are enormously different from the parents. The wool sower gall may be the leaf gall of this species because of its transient nature."  (See NC Link).
Look for them on white oak trees in the spring.  They don't cause any significant harm to the tree.  You can put a fresh wool sower gall in a plastic bag and wait for one to three weeks for the tiny wasps to emerge.  Keep it out of the direct sun so it doesn't cook, and remember that in spite of the name wasp, this family is totally harmless.

From North Carolina University

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