Backyard and Beyond

Recently, I glanced up at a sidewalk Common Hackberry/Celtis occidentalis I pass almost everyday. I noticed this for the first time.

Turned out there were a few others. These are the galls created by Pachypsylla venusta, the Hackberry Petiole Gall Psyllid. This is only the second time I’ve seen this species here in Brooklyn. There are a couple-three larval creatures inside these hard plant growths right now: see my other observation in Prospect Park.

This individual street tree hosts at least three species of gall. More than two dozen Celtis occidentalis galls are listed on gallformers.org, but this listing is missing at least one that I know of. They also include a leaf-spot disease that could confuse you.

Here’s what I’ve seen on this and other Common Hackberries around NYC:

Aceria celtis

Agromyza deserta

Ampelovirus hackberry-island-chlorosis (a leaf-spot disease, not a gall)

Celticecis spiniformis

Pachypsylla celtidisasterisca (not listed on gallformers, but fairly common in NYC)

Pachypsylla celtidisvesicula

Pachypsylla celtidismamma

Pachypsylla venusta

I will be helping out with Green-Wood Cemetery’s City Nature Challenge event on April 30th.

All my upcoming events can now be seen on my new Tours and Adventures page. Sign up early if you’re interested.