• Skip to main content
  • Skip to footer

Bonsai Tonight

An educational website about bonsai development

  • Blog
    • How-to Guides
  • Podcast
  • Shop
    • Bonsai
    • Books
    • Soil
    • Soil (wholesale)
    • Supplies
    • Tools
    • Video Consulting
    • Northern California Bonsai Resources
  • About
    • Workshops

Just in time for fall – pumpkin galls

September 18, 2020 by Jonas Dupuich

I’ve been curious about the small, round bumps that develop on the leaves of California live oaks for a while now. Some years I don’t see any, but most years a few show up toward the end of summer.

Pumpkin gall

Flattened round ball on a Coast live oak leaf

I’d worried they might be something that I don’t want on my trees, but Eric Schrader suggested they were leaf galls and not anything to be concerned about.

The suggestion was right on. The bumps are galls, specifically pumpkin galls. The culprit? Tiny wasps.

Oak leaf galls

New and old galls on an oak leaf

For those who are unfamiliar with gall development, it’s an interesting story.

Tiny wasps in the cynipid family, in this case, Dryocosmus minusculus, deposit eggs inside leaves that produce a substance that fools the plant into producing the gall material. The gall provides protection and nutrition for the developing baby wasp that bores through the gall wall when it’s mature.

Pumpkin gall

Nearly ripe pumpkin gall

As long as there aren’t many galls on an oak bonsai, there’s nothing to do about it beyond removing the galls or the infected leaves with your fingers. If gall development is widespread, it may be worth taking action.

I couldn’t find good suggestions for specific treatments, but the following best practices can help:

  • Keep oaks healthy – weak trees are more likely to be infected
  • Remove infected leaves
  • Remove branches with widespread damage (if the design allows for it)
  • Try a systemic pesticide or a contact spray (which will only be effective if applied when the wasps are laying eggs)

If you want to read up on galls, I found the information for this article here, here, and here. If you’re in the western U.S., a good book on the topic is the Field Guide to Plant Galls of California and Other Western States by Ronald A. Russo.

Do note that the pumpkin gall is just one of many galls that can infect our trees. If you have experience treating leaf, twig, or other galls on bonsai, let us know about it in the comments below!

✕

Subscribe to Bonsai Tonight

New Posts Delivered Every Tuesday and Friday

Success! Now check your email to confirm your subscription.

There was an error submitting your subscription. Please try again.

We won't send you spam. Unsubscribe at any time. Powered by ConvertKit

Filed Under: Bonsai Care Tagged With: Pests

Previous Post: « Wiring tip: how to prevent branches from splitting away from the trunk
Next Post: Bonsai Development Series #21: The effect of removing a sacrifice branch »

Reader Interactions

Comments

  1. Tino Mikosch says

    September 18, 2020 at 5:07 am

    Why not leave the galls and let the animals live?!

    • Jonas Dupuich says

      September 18, 2020 at 7:12 am

      Thanks for the note Tino – it’s fine to leave them alone when there are just a few, but if a tree is covered with leaf gall damage, it can stress or kill whole branches or trees.

  2. Bruce Williams says

    September 18, 2020 at 12:17 pm

    Thanks, very informative.

Footer

Follow Bonsai Tonight

Subscribe

Instagram ● Facebook ● Twitter
  • Blog
  • Podcast
  • Shop
  • About

P.O. Box 6560, Alameda, CA 94501 · 510-915-2025 · jonas (at) bonsaitonight (dot) com

© Copyright 2009-2023 Bonsai Tonight · All rights reserved · Privacy · Log in

This website uses cookies to improve your experience. You can opt-out if you wish. Accept Decline Read More
Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Non-necessary
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
SAVE & ACCEPT