It Takes Gall

Cynipids are tiny wasps known for their ability to create plant galls. The wasp lays its egg inside the plant tissue. The larva secretes substances that drastically alter the plant tissue for the benefit of the wasp. The outer appearance of the gall is characteristic of the wasp species.

The gall wasp larva is located in a chamber in the center of the gall. The larva secretes signals that induce the plant to make a layer of nutritive cells that surround the larval chamber. As the larva grows and feeds on the nutritive cells, adjacent cells will grow into new nutritive cells. Typically, the larval chamber and nutritive cells are separated from the rest of the plant by a layer of tissue. The outer tissues of the plant surrounding the gall are high in tannins and other plant defensive chemicals. The hard surface is deterrent to many predators and interlopers. However, some parasitoids are able to penetrate the gall defenses.

The nutritive cells provide the gall wasp with the high protein it needs to rapidly grow and develop. Gall wasps are commonly found on oak trees. Look for them this summer.

Oak galls

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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3 Responses to It Takes Gall

  1. Pingback: Jumping Galls | Living With Insects Blog

  2. Denise Haas says:

    they were on my burr oak seedling and I scraped them off. I was afraid that they would consume my tree and I would have to start over next spring with another tree. I am hoping that I did more good than harm.

  3. jjneal says:

    Scraping them off is ok.
    They should not cause much damage off or on.

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