This week’s episode is a rerun from the very early days of BOTW.

The BugLady loves it when the research she is doing makes a sharp turn toward History. 

Galls are mentioned by (very) early observers like the philosopher Theophrastus (371 to 287 B.C.) whose two botany books, Enquiry into Plants and On the Causes of Plants, influenced scientific thinking for the next 1500 years. People have been pondering the mysteries of galls for a long time, although not all of the hypotheses have been righteous ones. For example, because they were considered “supernatural growths,” galls were used to foretell the future. In the Middle Ages, their contents were examined (much tidier than chicken entrails). Spiders signaled pestilence; maggots meant either famine or a plague among cattle; flies – war; and ants – a bountiful harvest. In 1686 Malphigi suggested that galls were swellings that plants (like people) developed due to being stung by insects (but he straightened out and went on to discover capillaries and to have the Malphigian tube named after him). 

Last week’s BOTW, Galls 101, Galls I – Field Station, provided an introduction to the biology of galls and gall-makers. Short version: “Better living through chemistry.” This week’s BOTW features a few oak galls and a grape gall.  Remember, of the 2,000-plus kinds of galls found on North American plants, 800 different kinds form on oaks (genus Quercus). 

Cynipid wasps, which mainly target stems and leaves, are very big players in the oak gall game. The galls caused by some Cynipid wasps are very high in tannin/gallotannin (giving them the bitter taste that gave rise to their name, gall). Tannic acid is produced routinely by many plants (the plant’s strategy is to make itself unpalatable to grazers), but galls contain the highest tannin concentrations on most plants. It has been suggested that the gall-makers enjoy some “tannin-perks;” since tannins are somewhat anti-microbial, high-tannin galls may protect the larva against fungi and bacteria.

Interesting as they are to Nature Appreciators and to Scientists (they are, after all, “tumors” and their dynamic in that area is being studied), galls have a history of human commerce and use that goes back thousands of years. They have provided food, medicine, lamp fuel (in Greece, from a gall caused by a wasp named Cynips theophrastea), chemicals for tanning hides, dyes for fabric, leather and hair, beads for necklaces, and inks for tattooing and writing. 

Aleppo galls (produced by Cynips gallae-tinctoriae on certain Turkish/Eastern Bloc oaks) have the highest concentrations of tannin among the galls, 50 – 65%. Historically, Aleppo galls provided a strong astringent and a treatment for fevers, burns, mouth ulcers and toothache. They continue to be important trade item, now used more for tanning and dyeing and as an ingredient in inks. 

The presence of traces of iron-gall ink in the Dead Sea Scrolls makes for a pretty impressive pedigree. S.W. Frost, in Insect Life and Natural History, wrote in 1942 that “in some places, the law requires that permanent records be made with ink derived from gallnuts……The Aleppo gall has been specified in formulas for inks used by the US Treasury, Bank of England, German Chancellery, and the Danish Government.” The downside of iron-gall ink is the fact that it tends to fade after, oh, 1,500 years or so, and by that time, it may have discolored your paper, too. Google “oak gall ink” or “iron-gall ink” for the recipe; you can join the artists who explore older media – and the forgers of old documents – in reviving this ancient ink.

Oak-Apple Gall – There are about 100 kinds of these marble-to-ping-pong-sized galls; they grow on a leaf’s mid-vein or on the leaf stem (petiole). Some kinds have thin outer shells with fibrous insides, and others are denser. The oak apple pictured is occupied by a single larva. In fall, when you find these on the ground among the fallen oak leaves, check to see if there is a tiny exit hole and think about the size of the full-grown wasp that made it. Stokes, in Nature in Winter (great section on galls), tells of opening an oak apple gall that held about 200 ant eggs along with their nursery workers, and he has also found nests of mud wasps inside.

Oak Bullet Gall – Because they form from the woody tissue of the twig, these half-inch galls are very firm and can stay on a tree for several years. There are about 50 kinds of oak bullet galls, and some secrete a sticky “honeydew” that attracts other Hymenopterans- ants, bees and wasps. One source said that in exchange for the honeydew, the honeydew-eaters discourage parasitic wasps from laying their eggs in the galls. But, another source mentions attacks on bullet galls by parasitic wasps that insert their ovipositers into the gall and lay their egg on the gall-maker’s larva. Birds may peck open the gall and go after the larva.

Woolly Oak Leaf Gall – These attach to the mid vein (usually) or side veins (sometimes) and they look like cottonballs. They grow on the underside of the leaf, and they are easier to see as the leaves fall. Based on this one sample, it looks like they may have a “vampire-like” effect on some surrounding tissue.

Grape Phylloxera Gall – In 1850, there was only one species of grape being grown in all the vineyards of Europe.  In about 1860, the Grape Phylloxera (a wingless aphid about 1/20” long) was accidentally introduced from its native North America. The rest, as they say, is history. By 1880, the little critter had traveled to Australia, Algeria, South Africa, and via a different route, California.  One-third of French wine-producing grapes, about 2 ½ million acres, were wiped out (Mother Nature usually finds a way to deal with monocultures). 

While leaf galls seldom damage a plant, a plant with grape phylloxera leaf galls has root galls, too, and the root galls weaken and stunt the vine. The French fought back, and after burying live toads under the vines to draw out the poison failed to work (True!), they imported the rootstocks of resistant American Fox grapes both to graft the French vines onto and to develop hybrids from – all the while “dissing” the quality of the American grapes. Each of the leaf galls may house a teeny, yellow Aphid Mom and hundreds of eggs and/or nymphs.

Despite the galls and the withering, the leaf continues to function.

And by the way, it really bugs/galls the BugLady that much of the information about these generally harmless growths is found on sites that have a pest control and forestry-pest bias. The accounts invariably end with some variation of “These are harmless and don’t measurably damage the plant, but you don’t like the looks of them, so here are some chemicals you could throw at them.”

This concludes Galls I – How They Do That and Galls II – A Date with History.�� Coming eventually, Galls III – Oddball Galls.

Go outside – look for galls!

The BugLady

The post Galls II – Historic Galls Redux appeared first on Field Station.

Plant galls are swellings formed on the outsides of flowers, buds, leaves, veins, petioles, stems and/or trunks. Many are stimulated by animals, but some are caused by fungi and bacteria, and technically, the thickened bark tissue where two leaning trees rub against each other is a gall (technically, a raised wart or calloused area on human skin could be called a gall, too). Galls precipitated by animals appear on specific parts of specific hosts and are formed in distinctive shapes, and the names of the host and the gall-maker are often intertwined. Mites and insects (especially aphids, flies, and wasps) are the usual culprits.

Here’s the short version: a mite or an immature insect (or perhaps its mother, when she deposits it there) introduces chemicals to a plant that signal it to grow extra tissue. The mechanics of feeding may contribute, too. The tissue surrounds the bug, enclosing it in an edible shelter. Galls are pretty predator-resistant, though some parasitoids have figured it out, and some animals eat the whole gall. Leafier galls invite co-habitation by inquilines (from the Latin for “lodger” or “tenant”) – tiny insects looking for a place to squat, and perhaps for a meal. The tissue that will feed the tiny larva or nymph is also a prison, protecting the plant from any further peregrinations.

Most galls are smallish and thick-walled, which doesn’t leave much room for the gall-maker; by default, gall insects and mites are tiny, and since they don’t move around a lot, the younger stages may dispense with unnecessary parts like legs (here’s a ). Some galls are woody and persistent and can still be seen on plants in the next growing season, but new galls start to appear early as female gall-makers or their offspring take advantage of the new vegetation.

In general, gall-makers don’t damage their hosts, but there are some cosmetic effects, and sometimes the weight of the galls makes trees more susceptible to weather damage. The Catch 22 of gall control is that by the time the galls are apparent, the gall-maker is tucked inside, out of reach of pesticides. In order to get rid of unsightly leaves, you have to lop off branches.

This is not our first foray into galls; to travel back to where it all began, see /field-station/galls-i/,��/field-station/galls-ii/,��/field-station/galls-iii-oddball-galls/.

BASSWOOD SPINDLE/BUGLE/RED NAIL GALLS are caused by a mite named Eriophyes tiliae, family Eriophyidae ( ). The female mite overwinters in bark crevices and emerges as warming air summons the new leaves.�� She feeds on the tender leaves, and the galls that form have an entrance/exit hole on the . She will eventually mate within her gall, lay her eggs in it, and die. Her offspring mature in about two weeks and then leave the gall, dispersing on the wind or hitchhiking on other animals. Imagine the odds against a barely-mobile mite floating through the air and landing on the proper host plant!

If it does, and if the basswoods are still putting out new growth, there may be a second generation of galls; otherwise, the final generation will retire to bark shelters in fall. . Various species of Eriophyes mites target basswood, willow, cherry, maple, and even poison ivy, each producing a designer chemical that makes the characteristic gall.

HICKORY POUCH/LEAF STEM GALLS are caused by an aphid called Phylloxera caryaecaulis,��in the family (hickory trees are in the genus Carya�����Ի���caulis means stem). The name Phylloxera raises a bunch of red flags because a related aphid is a huge pest in vineyards – some European grape varieties were almost wiped out by this American aphid in the 1800’s but were saved by grafting them onto resistant American varieties (with, said the connoisseurs, a resulting decline in quality).

Anyway, the aphids overwinter as eggs, and a gall forms as a newly-emerged, wingless female feeds on the early leaves and petioles. Eventually, she lays eggs (remember, lots of aphids practice parthenogenesis during most of their life cycle – females give birth to more females, no males required). The nymphs, which will be winged, , and then the gall splits, releasing them. They lay more eggs, and these produce both males and females (insuring that the gene pool doesn’t get stagnant), and their eggs will overwinter.

Hickory pouch galls start out green, take on a reddish tinge as they age, and turn black after they split. These galls are not as innocuous as the basswood spindle galls – if a tree is young or is heavily infested with Phylloxera for successive years, branches may be weakened.

OAK ROSETTE GALLS are caused by a tiny wasp Andricus quercusfrondosus (Quercus is the genus of oak trees). Oaks host a lot of different galls, and many of them are formed by similar gall wasps/”gall flies” in the family Cynipidae.  The BugLady has been trying to track this one down for years – she finally found it as Andricus frondosa in “” — but she wasn’t able to find out very much about it. Oak rosette gall wasps use post, white, and bur oaks as hosts.

The gall-maker is a wasp larva that induces the plant to grow a dense cluster of small leaves, and it stays in the leafy gall throughout winter and exits in spring (along with its inquilines, which may include species of gall wasps that don’t make their own galls but find protection in others.’). Like aphids, some cynipid species are parthenogenic, and others alternate all-female generations with two-sex generations.

The CEDAR APPLE GALL (Gymnosporangium juniperi-virginianae) (Juniperus virginiana is the scientific name of eastern red cedar) is actually a rust; the gall is caused not by an arthropod but by a fungus, and it has an interesting life cycle.�� Finding the rust in its early stages is like finding a juniper dressed up in sea anemones.

It’s in a family of rust fungi called Pucciniaceae (the BugLady wonders whether the person who named this family was an opera fan). It’s a common rust in North America, and it needs two kinds of host trees to complete its life cycle – a juniper species and an apple species (including hawthorn, serviceberry, and crabapple).�� The fungus overwinters on the red cedar.

The orange-tentacled “anemone” appears with the spring rains, and the tentacles that produce spores (they’re called “gelatinous telial horns”) soon wither, but they’re capable of rehydrating a few times. Spores are blown to nearby apple trees, which get yellow spots on the upper surfaces of their leaves and eventually, bunches of tiny, spore-dispersing tubes or threads below ( ). The spores that are made on the apple trees are only able to grow if they land on a juniper, and the beat goes on. It may take two years after the return trip for the galls to form again on juniper.

Vocabulary word for the day – the study of the mechanics of galls and gall-makers is called cecidiology/cecidology, and the studier is called a cecidiologist/cecidologist.

Go outside – find some galls!

The BugLady

The post Galls VII appeared first on Field Station.

As veteran BugFans can attest, the BugLady is intrigued by galls. How many kinds are there? To quote from the first BOTW on galls (October, 2009) “Lawlor, in Discovering Nature Close to Home, states that North American plants support more than 2,000 kinds of galls – 800 different kinds form on oaks alone, about 125 kinds on roses, and more than 50 kinds on goldenrods (genus Solidago).”

So many galls, so little time.

What are galls? Here’s the quick and dirty explanation offered in a Wisconsin Extension vineyard report for Door County.

Gall formation in many instances is initiated by egg laying (oviposition) by the adult form of an insect or by feeding of early larval stages. Feeding by certain gall making insects results in the release of salivary fluids that may contain plant growth regulating substances (Auxins, IAA) and plant digesting enzymes, pectinases, proteases, and cellulases. The growth regulating substances released by feeding insects work in concert with the grapevines’ response to insect attack. The grapevines’ response to mechanical or chemical irritation is to isolate the toxins or invasion, resulting in a tumorous mass of tissue or gall.

In addition to galls caused by insects and mites (and nematodes), various fungi, bacteria, and viruses may cause galls on plants.

Many gall makers have complicated life cycles that, like the waterlily/reddish-brown plum aphids of recent BOTW fame, may include alternate hosts, and both sexual and asexual generations; in many cases, great chunks of their life histories are unknown. A gall maker tends to be named after the gall it makes.

The GRAPE FILBERT GALL is described in The Ohio Naturalist journal (December, 1914) as a “Bud gall, being a spherical mass 15-50 mm. diameter, of small, lozenge-shaped galls, each about 5 x 15 mm. Leaf-green, covered with a felty yellow or orange pubescence. Infrequent.”

It has been on our radar for some time – according to the 1916 Bulletin of the University of the State of New York,

Apparently the same gall is found on wild frost grape in Illinois and was described and figured by Messrs. Walsh and Riley in 1868. They state that the gall develops from a common center at a point where a [leaf] bud would ordinarily occur….. Large specimens of this gall bear a general resemblance to a bunch of filbert or hazelnuts as they grow on a bush, which led to the designation vitus-coryloides

(Vitus is the genus name for grapes, and Corylus is the genus name for filbert/hazelnut). Its cause is the Filbert gall maker midge now named Schizomyia coryloides, in the fly family Cecidomyiidae. For many galls, there’s not much information that is more recent than these century-old sources;

One of the big questions about galls is whether (other than cosmetically) they harm a plant. Sometimes. The larger, woodier, heavier galls that inhabit branch tips and persist for a year or more may weigh a branch down and make it more susceptible to wind and rain damage, but many of the smaller galls that grow on leafy tissue are nothing to worry about. Where would they be, after all, if they habitually killed their host plants? The Wisconsin Extension report concludes, “Galls may look destructive, but galls seldom injure the plant. Grapevines can support a large number of galls and still grow and reproduce normally ……. most galls that infect the soft tissue (leaves, tendrils, shoots) of grapevine are of little economic importance.”

ROUGH BULLET GALLS are woody, slightly elliptical galls that occur singly or in groups . As in many other oak galls, the gall maker is a tiny wasp – this one named Disholcaspis quercusmamma in the family Cynipidae (as Matthew Wills cheerfully informs us in his blog “Backyard and Beyond, “Why, yes, a translation of that would be “oak breasts.”). .

and almost immediately oviposits. The all-female (asexual) generation of this tiny wasp alternates with an even tinier sexual generation that hadn’t even been identified as recently as 2009, when researchers managed to rear some.

When the BugLady started photographing this gall, it was green and was attended by ants. Turns out that rough bullet galls are one of a number of species of galls that produce a sweet substance that, like aphid “honeydew,” attracts insects like bees and wasps. . The ants may be deterring both the insects that graze on oak leaves and the parasitic wasps that seek to lay their eggs in the gall. Honeydew-making galls are induced by just a few genera of Cynipid wasps. In her search, the BugLady came across some papers about hairstreak butterflies that feed on honeydew from galls and from scale insects. For BugFans who want to wander down that very interesting side road, see this article in the and .

A different Cynipid wasp, Andricus quercuspetiolicola (Quercus is the genus name of the oaks), makes the OAK PETIOLE GALL on various species of white oak. Unlike the bullet gall, this gall is produced in the softer tissue of the petiole (leaf stem), around the base of the leaf, and so it falls off when the tree loses its leaves. The gall starts growing in early spring, as the leaves start, and the gall makers exit by mid-summer. “BugTracks,” the website of Charley Eiseman, co-author of the excellent field guide Tracks and Signs of Insects and Other Invertebrates, has some amazing .

And – just when you thought you’d seen everything,

 
The BugLady

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