Gall in the context of Quercus

Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as each other's closest relative within Arachnida, rendering the group invalid as a clade. Most mites are tiny, less than 1 mm (0.04 in) in length, and have a simple, unsegmented body plan. The small size of most species makes them easily overlooked; some species live in water, many live in soil as decomposers, others live on plants, sometimes creating galls, while others are predators or parasites. This last type includes the commercially destructive Varroa parasite of honey bees, as well as scabies mites of humans. Most species are harmless to humans, but a few are associated with allergies or may transmit diseases.

The scientific discipline devoted to the study of mites is called acarology.

An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisphere, with some 500 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.

Ecologically, oaks are keystone species in habitats from Mediterranean semi-desert to subtropical rainforest. They live in association with many kinds of fungi including truffles. Oaks support more than 950 species of caterpillar, many kinds of gall wasp which form distinctive galls (roundish woody lumps such as the oak apple), and a large number of pests and diseases. Oak leaves and acorns contain enough tannin to be toxic to cattle, but pigs are able to digest them safely. Oak timber is strong and hard, and has found many uses in construction and furniture-making. The bark was traditionally used for tanning leather. Wine barrels are made of oak; these are used for aging alcoholic beverages such as sherry and whisky, giving them a range of flavours, colours, and aromas. The spongy bark of the cork oak is used to make traditional wine bottle corks. Almost a third of oak species are threatened with extinction due to climate change, invasive pests, and habitat loss.

Grape phylloxera is an insect pest of grapevines worldwide, originally native to eastern North America. Grape phylloxera (Daktulosphaira vitifoliae (Fitch 1855) belongs to the family Phylloxeridae, within the order Hemiptera, bugs); originally described in France as Phylloxera vastatrix; equated to the previously described Daktulosphaera vitifoliae, Phylloxera vitifoliae. The insect is commonly just called phylloxera (/fɪˈlɒksərə/; from Ancient Greek: φύλλον, leaf, and ξηρός, dry).

These almost microscopic, pale yellow sap-sucking insects, related to aphids, feed on the roots and leaves of grapevines (depending on the phylloxera genetic strain). On Vitis vinifera, the resulting deformations on roots ("nodosities" and "tuberosities") and secondary fungal infections can girdle roots, gradually cutting off the flow of nutrients and water to the vine. Nymphs also form protective galls on the undersides of grapevine leaves of some Vitis species and overwinter under the bark or on the vine roots; these leaf galls are typically only found on the leaves of American vines.

The goldenrod gall fly (Eurosta solidaginis), also known as the goldenrod ball gallmaker, is a species of fly native to North America. The species is best known for the characteristic galls it forms on several species in the Solidago, or goldenrod, genus. The fly's eggs are inserted near the developing buds of the plant. After hatching, the larvae migrate to an area below the plant's developing buds, where they then induce the plant's tissues to form into the hardened, bulbous chamber referred to as a gall. E. solidaginis’s interactions with its host plant(s) and insect, as well as avian, predators have made it the centerpiece of much ecological and evolutionary biology research, and its tolerance of freezing temperatures has inspired studies into the anti-freeze properties of its biochemistry.

In botany, a rosette is a circular arrangement of leaves or of structures resembling leaves.

In flowering plants, rosettes usually sit near the soil, but they can also be at the top of an otherwise leafless branch or trunk. Their structure is an example of a modified stem in which the internode gaps between the leaves do not expand, so that all the leaves remain clustered tightly together and at a similar height. Some insects induce the development of galls that are leafy rosettes.

Gall wasps, also traditionally called gallflies, or cynipids, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of cynipids are known worldwide, with about 360 species of 36 different genera in Europe and some 800 species in North America. Diplolepididae were traditionally included within the Cynipidae but have since been designated as their own family after some more recent phylogenetic studies.

An oak apple or oak gall is a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 2 to 4 centimetres (1 to 2 in) in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae.

Grape phylloxera is an insect pest of grapevines worldwide, originally native to eastern North America. Grape phylloxera (Daktulosphaira vitifoliae Fitch 1855) belongs to the family Phylloxeridae, within the order Hemiptera, bugs); originally described in France as Phylloxera vastatrix; it is equated to the previously described Daktulosphaera vitifoliae and Phylloxera vitifoliae. The insect is commonly just called phylloxera (/fɪˈlɒksərə/; from Ancient Greek: φύλλον, leaf, and ξηρός, dry).

These almost microscopic, pale yellow, sap-sucking insects, related to aphids, feed on the roots and leaves of grapevines (depending on the phylloxera genetic strain). On Vitis vinifera, the resulting deformations on roots ("nodosities" and "tuberosities") and secondary fungal infections can girdle roots, gradually cutting off the flow of nutrients and water to the vine. Nymphs also form protective galls on the undersides of grapevine leaves of some Vitis species and overwinter under the bark or on the vine roots; these leaf galls are typically only found on the leaves of American vines.

Root-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 species of plants worldwide are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss. Root-knot nematode larvae infect plant roots, causing the development of root-knot galls that drain the plant's photosynthate and nutrients. Infection of young plants may be lethal, while infection of mature plants causes decreased yield.

A domatium (plural: domatia, from the Latin "domus", meaning home) is a tiny chamber produced by a plant that may be occupied by arthropods.

Ideally domatia differ from galls in that they are produced by the plant rather than being induced by their inhabitants, but the distinction is not sharp; the development of many types of domatia is influenced and promoted by the inhabitants. Most domatia are inhabited either by mites or ants, in what can be a mutualist relationship, but other arthropods such as thrips may take parasitic advantage of the protection offered by this structure.

Apples appear in many religious traditions, often as a mystical or forbidden fruit. One of the problems identifying apples in religion, mythology and folktales is that as late as the 17th century, the word "apple" was used as a generic term for all (foreign) fruit other than berries, but including nuts. This term may have extended to plant galls such as oak apples, as they were thought to be of plant origin. When tomatoes were introduced into Europe, they were called "love apples". In one Old English work, cucumbers are called eorþæppla (lit. "earth-apples"), just as in French, Dutch, Greek, Hebrew, Afrikaans, Persian and Swiss German as well as several other German dialects, the words for potatoes mean "earth-apples". In some languages, oranges are called "golden apples" or "Chinese apples". Datura is called "thorn-apple".

At times artists co-opted the apple, whether for ironic effect or as a stock element of symbolic vocabulary. Thus, secular art as well made use of the apple as symbol of love and sexuality. It is often an attribute associated with Venus who is shown holding it.

Quercus infectoria or the Aleppo oak is a species of oak well known for producing galls (called manjakani in Malaysia, majuphal in India) that have been traditionally used for centuries in Asia medicinally while also used in softening leather and in making black dye and ink.

Disholcaspis quercusmamma, the oak rough bulletgall wasp, is a species of gall wasp in the family Cynipidae. The quercus in its name is the genus name for oak, while "mamma" is Latin for "breast", presumably a reference to the "nipple" on the gall.

The galls formed by several species in the Disholcaspis genus are called "bullet galls" due to their shape and size. Disholcaspis quercusmamma galls are similar in appearance to those formed by Disholcaspis quercusglobulus; the distinguishing characters are a velvety surface and pointed apex ("nipple").