Posts Tagged 'galls'

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.

Galls

You may know of my fascination with galls, the structures created by plants in response to insects. In the Botanisk Have in Copenhagen and in the Alnapsparken at Sveriges Lantbruksuniversitet, the Swedish agricultural college, I found these lovely knopper oak galls. They were growing on acorns of Quercus robur, the great oak of Europe, which we usually call the English Oak (cf. hearts thereof), but when in Rome, or more specifically Sweden, it’s skogsek. It is, of course, thanks to a Swede, one Carl von Linne — the family name comes from the lime (linden) trees on the family estate — who is better known as Linnaeus, who codified the binomial naming system that is supposed to be universal. So the full binomial for this oak is Quercus robur L., the initial standing for the namer, yup, Linnaeus. One of L.’s students was the founder of the precursor institutions of the SLU.A gall wasp, Andricus quercuscalicis, causes these oaks to form these when they lay their eggs on the emerging acorns. These wasps need Turkey Oaks (Quercus cerris L.) to complete their life cycle, so finding them in botanical garden settings makes a lot more sense then finding them out in the “wild,” where these other oaks are a lot less common (Q. cerris is native to southeastern Europe and Anatolia/Asia Minor).

Galls like these are full of tannin, a gallic acid which has been used for centuries as a component of iron gall ink. The Magna Carta, Beowulf, and the Lindisfarne gospels were all written in this stuff, which is made from the galls (Oak Apple galls in these cases), iron sulfate, and water.

Galls

A tell-tale growth. Turn the leaf over.The gall of it all! I am fascinated by these things. Galls are created by the plant in response to the agitation of a wasp, mite, or something even smaller. For instance, insects lay their eggs on or in the plant, the plant is stimulated to build up over the eggs. It is a process of containment and isolation. For the gall-forcer, it’s protection and food. The eggs will hatch out to larvae in the gall. The critters will find themselves inside a plant! And that, of course, can be eaten.Eventually the critters will emerge, boring out, unless something gets them first. This one looks like it may have been opened up by a predator. A bird?

*

Another kind of gall: as a crime family, the Trumps have long connections with mafias of various sorts. Bloomberg on the Russian criminal front.

 

 

*

Oak Galls

gall1The mighty oaks and their galls are an endless source of curiosity. This particular type, a hard, fruit-like structure, is created by a tiny wasp, which essentially irritated the tree into making them for their larva.
galls2Clever boots! The trees are Swamp White Oak (Q. bicolor), according to the Street Tree Map. (I’m waiting on some leaves to see if I can confirm that.)gall3The wasp’s exit hole. I think these are Disholcaspis genus gall wasps. D. quercusmamma perhaps? (Why, yes, a translation of that would be “oak breasts.”)


Share

Bookmark and Share

Join 590 other followers

Twitter

Nature Blog Network

Archives