Nine-Minute Naturalist: What a Galling Spring

By Samuel Fuqua,

  Filed under: Nine-Minute Naturalist
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What a Galling Spring

by Josh Palumbo, Forest Management Coordinator

I welcome you to The Nature Foundation at Wintergreen’s attempt to bring some nature and knowledge into your home. The Nine Minute Naturalist borrows from NPR’s lovely 90-Second Naturalist podcast. Since we all have a bit more time on our hands, the goal is to take something that is happening out in our environment and stimulate your brain for roughly nine minutes. Don’t let something as “minor” as a quarantine to keep you from learning. I hope you enjoy!


Spring means new, rapid plant growth throughout the mountain resulting in an abundance of flowers, fruit and possibly galls. The spring of 2020 has been galling or vexing for so many and now the time has come for plants to be galled. Galls are abnormal growths of plant tissue induced by insects and other organisms. Throughout Wintergreen, plants are being used by hosts for a variety of organisms creating unique forms that are easy to identify.

One of the most common galls at Wintergreen is the Oak Apple gall. Oak Apple galls are green golf ball shaped growths with a thin shell and a spongy core. These galls are created by Oak Apple wasps that inject an egg into the midrib of a leaf and chemically trick the tree into growing a protective shell over the developing larvae. The larvae will use the tree growth for browse as it grows. The gall is often used by other insects to host their larvae, sharing the space with the growing wasp. As the season progresses the gall will change to brown in color and harden. Despite appearing woody with age, the gall is a modified leaf. The good news is this gall does not injure the tree. Heavy infestation of Oak Apple gall may cause premature leaf drop.

Spindle galls are another gall found on a variety of trees throughout the mountain. The cause of this gall is the Eriophyid mite. The gall causes odd deformations in the form of spiky growths off the upper surface of the leaf. It is most commonly found on cherry and maple trees at Wintergreen. The mites trick the trees to grow around the larvae serving as both residence and dinner. Despite the appearance of being loaded with galls, the tree is not injured. Treatment of these galls is not recommended.

Cedar-apple rust is another tree issue throughout Wintergreen that is easily identified. This fungus is most commonly found on eastern red cedar and forms hard woody galls covered in gooey orange fungal growth. This rust can also be found on apple, hawthorns and serviceberry. It rarely causes damage to the host but certainly is not appealing to the eye. They do occasionally cause damage to fruit of the apple, hawthorn or serviceberry tree.

So when you feel that this spring can’t be any more galling to you, know that spring is the time for galls at Wintergreen. If you have a growth or insect that is affecting your plants, feel free to send pictures to forestmanage@twnf.org and I can assist in identification and treatment options.

 

 

 

Oak Apple gall

 

Spindle gal

 

Cedar-apple rust

 

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