Galls: Amazingly Diverse and Fascinating Plant Growths

Have you ever found a leaf with weird little balls or spiky things attached to it? Or found a plant with a weird growth on its stem or a dense clump of leaves growing out of an odd place? Chances are those were galls.

Going into this conversation, I knew a little bit about galls, but not much. However, what I knew was pretty interesting. So I wanted to learn more, and I thought you might be interested in learning more about them too. My mind was almost instantly blown. Galls are so much more diverse, interesting, and amazing than I ever dreamed of.

Louis Nastasi joined me for this conversation. Louis is a PhD candidate at Penn State's Frost Entomological Museum which is Penn State's research collection of insects and other arthropods. His research is looking at gall wasps in prairie plants, particularly Silphiums, of the Midwest.

At its most basic level, a gall is a piece of plant tissue that has been modified by the activity of another organism. However, in reality, galls are so much more than that implies. They can be formed by a variety of different organisms, although most of the ones we think about and encounter are formed by different types of insects. They can also be found in a variety of different places on the plant, including hidden inside the stem in such a way that you would never know it was there unless you cut the stem open.

Louis and my conversation touches on all kinds of topics related to galls. We start out talking a little about what galls are and the types of organisms that can form them, then focus more on insect-induced galls. From there our conversation covers topics like why insects might choose to form a gall in this plant over that plant, the importance of galls and the ecosystem, and how little we actually know about galls.

This was a really fun and educational conversation. I learned so much and am completely intrigued. I could have kept discussing and learning more about galls for much longer because they are so much more complex and interesting than I realized. I hope you find the conversation as interesting and educational as I did. I also encourage you to check out the resources that Louis shared with us.

Links:

• Louis's contact info:
  • Email: LFN5093@PSU.edu
  • Twitter: https://twitter.com/toomanywasps
• Louis's wasp I.D. course: https://waspidcourse.wordpress.com
• An example of a new state record of a gall wasp that was posted on i-Naturalist: https://www.inaturalist.org/observations/117815477
• Field Guide to the Herb and Bramble Gall Wasps of North America by Louis F Nastasi and Charles K Davis: https://scholarsphere.psu.edu/resources/1acfec30-7e4d-4130-98f5-46ab75972e08
• Other resources Louis recommends:
  • Gall Formers: https://gallformers.org/
  • Gall wasp page on BugGuide: https://bugguide.net/node/view/14878
  • i-Naturalist: https://inaturalist.org/
• Related Backyard Ecology articles and episodes:
  • The Goldenrod Gall Fly: An Insect with a Fascinating Life History and Valuable Role in the Ecosystem: https://www.backyardecology.net/the-goldenrod-gall-fly-an-insect-with-a-fascinating-life-history-and-valuable-role-in-the-ecosystem/
  • An Introduction to iNaturalist with Maddy Heredia: https://www.backyardecology.net/an-introduction-to-inaturalist-with-maddy-heredia/
• Backyard Ecology Website: https://backyardecology.net
• Backyard Ecology YouTube Channel: https://www.youtube.com/backyardecology
• Backyard Ecology Blog: https://www.backyardecology.net/blog/
• Backyard Ecology Patreon page: https://www.patreon.com/backyardecology
• Subscribe to Backyard Ecology emails: https://www.backyardecology.net/subscribe/

Episode image:

• A gall on a leaf.
• Photo credit: Andy Deans, all rights reserved