Two gall species on Boxelder Maple

This spring I was excited to find two species of gall on a group of Boxelder Maple saplings on the edge of the Freshwater Wetland in Randalls Island, Manhattan, NYC.

On the Boxelder Maple there, the most common gall (extremely common this spring!) is the "Box Elder Pouch Gall Mite" (caused by mites). The mites create galls that look like little nodules on the upper leaf surface (see images one and two).

However, there were also some galls (not nearly as many) which were a lot larger, and looked like a soft pale money bag (but they were quite hard). These galls occurred on the rib of a leaflet (see the third image).

Here are my two other observations of other examples of that larger gall:

https://www.inaturalist.org/observations/24764347

https://www.inaturalist.org/observations/24764268

And here is a gall on BugGuide that looks like those big ones:

https://bugguide.net/node/view/532163/bgimage

It turns out that the big galls are indeed caused by "Box Elder Gall Midge", Contarinia negundinis, which is in the Family Cecidomyiidae - Gall Midges and Wood Midges.

So I thought that was cool, simultaneously finding some galls caused by mites, and some galls caused by midges on the same species of plant.

Thank you to some input from Charley Eiseman.

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.................................INTERESTING UPDATE FROM AUGUST 2019:

In August I noticed some strange little pink granular clusters on some of the young leaves which also had the Box Eldger Pouch Gall Mite galls:

https://www.inaturalist.org/observations/31812587

Then @megachile suggested that perhaps the pink clusters could be Maple Erineum Mite (Aceria calceris). He said that "The Amrine catalog says that Aceria calaceris, which causes red erineum on Acer glabrum, was reported on boxelder too. Amrine notes that he thinks it's probably a mistake but that is a possibility."

Posted on May 20, 2019 01:58 PM by susanhewitt