Those aren’t just warts - They’re Hackberry Psyllids!
While walking around your neighborhood park, whether it be for exercise, for socialization, or just for the sake of getting outside, you may have noticed some abnormal warty growths on the leaves of some trees.
Image of galls, by megsf on iNaturalist, some rights reserved.
These warts, called galls, actually house a big secret. More of a little secret, really. Meet the hackberry psyllid. When these psyllids hatch from their eggs as larvae, they begin to suck the juices from the leaves of hackberry trees. The tree responds to the larvae’s ravenous behaviour by forming a gall around the larvae, where they stay until the late summer or early fall, when they break free from their galls as fully grown adults.
An adult hackberry psyllid. Image by Missouri Department of Conservation.
Oddly enough, despite having wings, the hackberry psyllid can’t fly, but opts to jump from plant to plant. These winged hopping wonders are pretty hard to spot too, as they grow to a length of 2-6 millimetres.
An interesting fact about hackberry psyllids is that there are numerous different species of them, each quite similar in appearance, but are distinguished by the shape of their galls. At one point, scientists confused multiple different species of hackberry psyllid for the same species because of how similar their physical appearance was to each other.
A very common species of hackberry psyllid that you can find in southern Ontario is the Hackberry Nipplegall Psyllid, named after the round, bubble-like shape of their galls.
A wide variety of insects induce galls in plants. Some additional local species to explore include the Goldenrod Gall Fly and Willow Pinecone Gall Midge.
Next time you’re out and about, keep an eye out for those unique bumps, because each one contains its very own bug resident just waiting to take wing.
Reference
Missouri Department of Conservation. https://mdc.mo.gov/discover-nature/field-guide/hackberry-psyllids-hackberry-nipple-gall-makers
Written and researched by Noah Leach. Noah is a Grade 12 student who enjoys hiking, the environment, and all things Biology. He completed a co-operative program placement with EcoSpark this spring for his high school in Toronto District School Board.