Posts Tagged 'galls'

More Galls

I found a mother-of-gall tree! A red oak, Quercus rubra, in Green-Wood. This tree was probably brought in as a sapling a few years ago. I wonder where it was raised? Could it be that the gall-making species came in with the tree, as we’ve seen with lichens transported into the city on saplings destined to be street trees?
Everything pictured in today’s post was on this one oak — two very nearby red oaks, both looking like they were planted this year or last, were devoid of this diversity. They only had one type of gall on them.
How many gall-makers are seen here? Three, four?
Is this, for instance, one or two gall species at work?
Oops, here’s another.
And another.

Getting very little traction on iNaturalist with identification for these things. There are too many galls and not enough people interested in them.

And yet, consider the fascinating relationships of insect (wasp, mite) and plant. (And not just insects!) The plant forms these structures, which are unlike anything else they produce in the normal course of events, in response to the animal. The animal uses the plant for shelter and food, and some other animals may use the first animal, parasitizing the egg or larva inside the gall. And around and around it goes.

Monday Galls

Gallia est omnis divisa in partes tres
At the tips of a young oak, small round nestled in filamenty nests. Galls (not Gauls, pace Casesar) with exit holes. Big question in the wonderful world of galls is: what emerged, the gall inducer or the inquiline (parasite)?

Not just on the bud tips.

Possibly something in the Andricus gall wasp genus. This is a large genus. As I understand it, each species makes a unique gall. These tiny wasps stimulate the tree by chemical commands and the tree grows a gall in response. The tree is being hijacked, but not really damaged (?).

But wait! I’d originally thought this tree was a red oak but could it be be a bur oak? Will have to double check this.

If it’s a bur, then Andricus quercusfrondosus sounds like a possibility. This source notes that this species creates autumnal growths for the the agamic or asexual generation. Yes, gall wasps, which were once all called gall flies, alternate an asexual generation and a sexual generation. According to the cited piece, the agamic or sexual generation isn’t known for this species.

More complications: found a similar if not same gall on a definite red oak, which will be the subject of another day.

To summarize: galls are complicated.

Galls Again

Yes, it’s time for a Fall Gall edition. These are the structures created by the tree, in this case, in response to insects (in these cases) who lay their eggs on the tree. This one is, I think, a Hedgehog Gall.
Not sure on this species.
Nor this. This one was much smaller and looked like felt.

This one white oak in Green-Wood has at least four gall-forcing species on it. These three were evidenced on fallen leaves and twigs. (Here’s the fourth.)

Gallish

Went on a walk last weekend in Central Park in honor of Alexander Von Humboldt and the late mycologist Gary Lincoff. We met at the Explorer’s Gate, next to the Humboldt bust. The baby vomit stench of ginkgo fruits, rotting and crushed on the sidewalk, deterred us not.

The venerable American elm behind Alex reaches over the wall to the right and sends branches well below the street level down below to the park level. It’s cosseted by cables linking the outstretching limbs. It’s a good metaphor for the park itself: it takes a lot of support to keep this going, to handle the millions who pour into its bounds every year.

Seen amidst the conversations:
A very pale Mallard variation, presumably a feral domesticated bird.
New York City, baby! Big as a Sherman Tank and just a few feet away from the second most crowded bridge in the park.
Hackberry Star Gall, caused by a psyllid, Pachypsylla celtidisasterisca, a kind of true bug.

Same Oak, Different Gall

Looking a bit like mushrooms, these galls on the leaves of this white oak in Green-Wood are the results of yet another Cynipidae gall wasp, Phylloteras poculum. Mine was the third iNaturalist report of this species. I tracked the species down on bugguide.net. Bugguide.net doesn’t have an image of the actual (tiny) wasp.

So this one oak tree has a minimum of three different galls on it.

Galls of It All

So it seems we still aren’t quite sure how galls are created. Something irritates a plant; the plant responds by creating a unique growth. The hundreds of species of tiny gall wasps are the best known gall-forcers, but other insects (aphids, mites, others) and some microbial forms do it, too.

But let’s stick with the tiny gall wasps. (This is a simplistic description, go here for more detail.) They lay an egg on the plant’s leaf or stem. The plant responds by growing around the egg or larva which digs into the plant. Each resulting growth, or gall, is unique to the species of gall-making agent that initiates it. It’s a chemical process, a benign hijacking of the plant’s growth. The sphere on the oak above is sort of a highly modified leaf. The insect larva within is protected by this structure from hungry predators (but parasites can still get in). The gall is also food for the larva. The plant doesn’t seem to be harmed. The wasp emerges from the gall to start all over again, sometimes with an intervening stage elsewhere on the same tree.
Here are all my posts on galls over the years. All the galls in this post are on white oaks. Oaks and galls are a time-honored combination. In North America, 800 gall wasp species are associated with oak trees. The first two pictures are of a beautiful spherical gall on a big shaggy specimen. The rest of these examples were found on a much younger tree. In this case, they’d fallen out of the tree.The only ones I can identify for certain are the Hedgehog Galls, made by the Hedgehog Gall Wasp. But is this red one a new Hedgehog or something all together different?

***
“The level of disconnection from nature seemed independent of where children lived.” A new study suggests rural and urban American kids get all their nature information from TV, the internet, and those moronic computer games, and they are not the better for it. (Surprise!) Please share your love of the wild — including galls — with your children and grandchildren, nieces, nephews, etc. They’re not going to get it anywhere else.

Hedgehog Galls

Why, they’re miniature Tribbles! This white oak has been hosting these structures for years now on its leaves. But this is the first time I’ve seen them so fresh. They’ll brown up over the summer.A tiny wasp, Acraspis erinacei, known as the Hedgehog Gall Wasp, creates these in conspiracy with the tree. Essentially the wasp hijacks the tree’s chemistry to protect its young. The tree is not harmed. Come the fall, females will emerge from these and lay their eggs on the oak’s buds. Those bud gall wasps will emerge next year and start the process all over again by moving to the leaf.

All the galls on the blog.


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