# Gall

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Abnormal growths especially on plants induced by parasitic insects and other organisms

This article is about the abnormal growths in plants. For other uses, see [Gall (disambiguation)](/source/Gall_(disambiguation)).

[Cola-nut galls](/source/Cola-nut_gall) (*[Andricus lignicola](/source/Andricus_lignicola)*) on [pedunculate oak](/source/Pedunculate_oak), caused by a cynipid [gall wasp](/source/Gall_wasp)

**Galls** (from the [Latin](/source/Latin) *galla*, 'oak-apple') or ***cecidia*** (from the Greek *kēkidion*, anything gushing out) are a kind of swelling growth on the external [tissues](/source/Tissue_(biology)) of plants. Plant galls are abnormal outgrowths[1] of [plant](/source/Plant) tissues, similar to [benign tumors](/source/Benign_tumor) or [warts](/source/Wart) in animals. They can be caused by various [parasites](/source/Parasite), from [viruses](/source/Virus), [fungi](/source/Fungi) and [bacteria](/source/Bacteria), to other plants, [insects](/source/Insect) and [mites](/source/Mite). Plant galls can be such highly organized structures that their cause can be determined without the actual agent being identified. This applies particularly to insect and mite plant galls. The study of plant galls is known as cecidology.

## Taxonomic range

Plant galls are caused by a wide range of organisms, including animals such as insects, mites, and nematodes; fungi; bacteria; viruses; and other plants.

### Insects

Further information: [List of insect galls](/source/List_of_insect_galls)

Insect galls are the highly distinctive plant structures formed by some [herbivorous](/source/Herbivore) insects as their own microhabitats. They are plant tissue which is controlled by the insect. Galls act as both the habitat and food source for the maker of the gall. The interior of a gall can contain edible nutritious starch and other tissues. Some galls act as "physiologic sinks", concentrating resources in the gall from the surrounding plant parts.[2] Galls may also provide the insect with physical protection from predators.[3][4]

Insect galls are usually induced by chemicals injected by the [larvae](/source/Larva) of the insects into the plants and possibly mechanical damage. After the galls are formed, the larvae develop inside until fully grown, when they leave. To form galls, the insects must take advantage of the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.

The [meristems](/source/Meristem), where plant cell division occurs, are the usual sites of galls, though insect galls can be found on other parts of the plant, such as the leaves, [stalks](/source/Plant_stem), [branches](/source/Branch), [buds](/source/Bud), [roots](/source/Root), and even [flowers](/source/Flower) and [fruits](/source/Fruit). Gall-inducing insects are usually species-specific and sometimes tissue-specific on the plants they gall.

[Gall-inducing insects](/source/Gall-inducing_insect) include [gall wasps](/source/Gall_wasp), [gall midges](/source/Gall_midge), [gall flies](/source/Tephritidae), [leaf-miner flies](/source/Agromyzidae), [aphids](/source/Aphid), [scale insects](/source/Scale_insect), [psyllids](/source/Psyllid), [thrips](/source/Thrips), gall moths, and [weevils](/source/Curculionidae).[5]

Many gall insects remain to be described. Estimates range up to more than 210,000 species, not counting [parasitoids](/source/Parasitoid) of gall-forming insects.[6]

#### Cynipid wasps

Main article: [Gall wasp](/source/Gall_wasp)

More than 1400 species of cynipid wasps cause galls. Some 1000 of these are in the tribe [Cynipini](/source/Cynipini), their hosts mostly being [oak](/source/Oak) trees and other members of the [Fagaceae](/source/Fagaceae) (the beech tree family).[6] These are often restricted taxonomically to a single host species or a group of related species.

	- Cynipid wasp galls

		- [Oak artichoke gall](/source/Oak_artichoke_gall) caused by *[Andricus foecundatrix](/source/Andricus_foecundatrix)*

		- Artichoke gall cut open to reveal wasp larva

		- [Knopper gall](/source/Knopper_gall) caused by *[Andricus quercuscalicis](/source/Andricus_quercuscalicis)*

		- Oak gall caused by *[Neuroterus albipes](/source/Neuroterus_albipes)* forma *laeviusculus*

		- Marble gall of oak caused by *[Andricus kollari](/source/Andricus_kollari)*

		- Cherry oak gall caused by *[Cynips quercusfolii](/source/Cynips_quercusfolii)*

		- Cherry oak gall cut open to reveal wasp larva

		- Cherry oak gall wasp adult

		- [Red-pea gall](/source/Red-pea_gall) (*Cynips divisa*) on [pedunculate oak](/source/Pedunculate_Oak)

		- *[Kokkocynips rileyi](/source/Kokkocynips_rileyi)* oak gall

		- *[Phylloteras poculum](https://en.wikipedia.org/w/index.php?title=Phylloteras_poculum&action=edit&redlink=1)* oak galls

#### Non-cynipid wasps

Some wasps from other groups, such as the [Diplolepididae](/source/Diplolepididae) and the [Chalcidoidea](/source/Chalcidoidea), also cause plant galls.

	- Non-cynipid wasp galls

		- Rose bedeguar gall on a [wild rose](/source/List_of_Rosa_species), caused by *[Diplolepis rosae](/source/Diplolepis_rosae)*, a [diplolepid](/source/Diplolepididae) wasp

		- Section through young bedeguar gall showing wasp larvae and cells

		- Gall on [Eucalyptus](/source/Eucalyptus) due to [chalcid wasp](/source/Chalcid_wasp) *[Leptocybe invasa](/source/Leptocybe_invasa)*, India

#### Hemipteran bugs

Among the [hemipteran](/source/Hemiptera) bugs that cause galls are the [psyllid](/source/Psyllidae) bug *[Pachypsylla celtidisumbilicus](https://en.wikipedia.org/w/index.php?title=Pachypsylla_celtidisumbilicus&action=edit&redlink=1)*, and the [woolly aphid](/source/Woolly_aphid) *[Adelges abietis](/source/Adelges_abietis)*, which parasitises [coniferous](/source/Conifer) trees such as the Sitka spruce and the Norway spruce.

	- Hemipteran galls

		- Developing pineapple pseudocone galls on [Norway spruce](/source/Norway_spruce), caused by woolly aphid *[Adelges abietis](/source/Adelges_abietis)*

		- Pineapple gall cut open to show the woolly aphid larvae inside

		- [Pineapple gall](/source/Pineapple_gall) on [Sitka spruce](/source/Sitka_spruce) caused by *Adelges abietis*

		- *[Pachypsylla celtidisumbilicus](https://en.wikipedia.org/w/index.php?title=Pachypsylla_celtidisumbilicus&action=edit&redlink=1)* hackberry gall

#### Dipteran flies

Some [dipteran](/source/Diptera) flies such as the [cecidomyiid](/source/Cecidomyiidae) gall midges *[Dasineura investita](/source/Dasineura_investita)* and *[Neolasioptera boehmeriae](/source/Neolasioptera_boehmeriae)*, and some [Agromyzidae](/source/Agromyzidae) leaf-miner flies cause galls.

	- Midge galls

		- Gall of *[Japanagromyza](/source/Japanagromyza) inferna* ([Agromyzidae](/source/Agromyzidae)) in *[Centrosema virginianum](/source/Centrosema_virginianum)*

		- Nettle gall caused by *[Dasineura investita](/source/Dasineura_investita)* ([Cecidomyiidae](/source/Cecidomyiidae))

		- False nettle stem gall caused by gall midge *[Neolasioptera boehmeriae](/source/Neolasioptera_boehmeriae)* ([Cecidomyiidae](/source/Cecidomyiidae))

		- *[Schizomyia impatientis](/source/Schizomyia_impatientis)* ([Cecidomyiidae](/source/Cecidomyiidae)) jewelweed flower gall

		- *[Phytoliriomyza pittosporophylli](/source/Phytoliriomyza_pittosporophylli)* ([Agromyzidae](/source/Agromyzidae)) galls in leaf of *[Pittosporum undulatum](/source/Pittosporum_undulatum)*

### Mites

[Mites](/source/Mites) in the family [Eriophyidae](/source/Eriophyidae) often cause galls to form on their hosts. The family contains more than 3,000 described species which attack a wide variety of plants.

	- Mite galls

		- Lime nail galls caused by the mite *[Eriophyes tiliae](/source/Eriophyes_tiliae)*

		- Galls on [purple coneflower](/source/Purple_coneflower) caused by an undescribed mite species

		- Poison ivy leaf galls caused by *[Aculops rhois](/source/Aculops_rhois)*

### Nematodes

[Nematodes](/source/Nematode) are microscopic worms that live in soil. Some nematodes (*Meloidogyne* species or [root-knot nematodes](/source/Root-knot_nematode)) cause galls on the roots of susceptible plants. The galls are often small.[7][8]

	- Nematode galls

		- Juvenile *[Meloidogyne](/source/Meloidogyne)* penetrating a host plant

		- Root-knot galls caused by the nematode *[Meloidogyne](/source/Meloidogyne)*

### Fungi

Many [rust fungi](/source/Rust_fungi) induce gall formation, including [western gall rust](/source/Western_gall_rust), which infects a variety of [pine](/source/Pine) trees, and [cedar-apple rust](/source/Gymnosporangium). Galls are often seen in *[Millettia pinnata](/source/Millettia_pinnata)* leaves and fruits. Leaf galls appear like tiny clubs; however, flower galls are globose. *[Exobasidium](/source/Exobasidium)* often induces spectacular galls on its hosts.

The fungus *[Ustilago esculenta](/source/Ustilago_esculenta)* associated with *Zizania latifolia*, a wild rice, produces an edible gall highly valued as a food source in the [Zhejiang](/source/Zhejiang) and [Jiangsu](/source/Jiangsu) provinces of China.[9]

	- Fungal galls

		- Gall on conifer *[Juniperus virginiana](/source/Juniperus_virginiana)* caused by [Gymnosporangium](/source/Gymnosporangium) ([Pucciniales](/source/Pucciniales))

		- Leaf galls on *[Rhododendron ferrugineum](/source/Rhododendron_ferrugineum)* caused by fungus *[Exobasidium](/source/Exobasidium) rhododendri*

### Bacteria and viruses

Gall-causing bacteria include *[Agrobacterium tumefaciens](/source/Agrobacterium_tumefaciens)* and *[Pseudomonas savastanoi](/source/Pseudomonas_savastanoi)*.

Gall forming virus was found on rice plants in central Thailand in 1979 and named rice gall dwarf. Symptoms consisted of gall formation along leaf blades and sheaths, dark green discoloration, twisted leaf tips, and reduced numbers of tillers. Some plants died in the glasshouse in the later stages of infection. The causal agent was transmitted by the hemipteran bug *[Nephotettix nigropictus](/source/Nephotettix_nigropictus)* after an incubation of two weeks. Polyhedral particles of 65 nm diameter in the cytoplasm of phloem cells were always associated with the disease. No serologic relationship was found between this virus and that of rice dwarf.

	- Microbial pathogen galls

		- Crown gall on *[Kalanchoe](/source/Kalanchoe)* infected with *[Agrobacterium tumefaciens](/source/Agrobacterium_tumefaciens)*

		- Citrus vein enation woody gall on *[Fortunella japonica](/source/Fortunella_japonica)* caused by a pathogen with an aphid [vector](/source/Vector_(parasitology))

### Plants

The [hemiparasitic](/source/Hemiparasitic) plant [mistletoe](/source/Mistletoe) forms woody structures sometimes called galls on its hosts.[10] More complex interactions are possible; the parasitic plant *[Cassytha filiformis](/source/Cassytha_filiformis)* sometimes preferentially feeds on galls induced by the cynipid wasp *[Belonocnema treatae](/source/Belonocnema_treatae)*.[11]

## Uses

Galls are rich in [resins](/source/Resin) and [tannic acid](/source/Tannic_acid) and have been used widely in the manufacturing of permanent [inks](/source/Ink) (such as [iron gall ink](/source/Iron_gall_ink)) and astringent ointments, in [dyeing](/source/Dyeing), and in [leather tanning](/source/Tanning_(leather)). The [Talmud](/source/Talmud)[12] records using [gallnuts](/source/Gallnut) as part of the tanning process as well as a dye-base for ink.

Medieval [Arabic](/source/Arabic_language) literature records many uses for the gall, called عفص *ˁafṣ* in Arabic. The [Aleppo gall](/source/Oak_marble_gall), found on [oak](/source/Oak) trees in northern [Syria](/source/Syria), was among the most important exports from Syria during this period, with one merchant recording a shipment of galls from [Suwaydiyya](/source/Port_Saint_Symeon) near [Antioch](/source/Antioch) fetching the high price of 4½ [dinars](/source/Dinar) per 100 pounds. The primary use of the galls was as a [mordant](/source/Mordant) for black dyes; they were also used to make a high-quality ink. The gall was also used as a medication to treat [fever](/source/Fever) and [intestinal](/source/Intestine) ailments.[13]

## See also

- [British Plant Gall Society](/source/British_Plant_Gall_Society)

- [Forest pathology](/source/Forest_pathology)

- [List of insect galls](/source/List_of_insect_galls)

Similar structures (not galls):

- [Burl](/source/Burl)

- [Witch's broom](/source/Witch's_broom)

## References

1. **[^](#cite_ref-1)** ["gall(4)"](https://www.merriam-webster.com/dictionary/gall). *Merriam-Webster Online Dictionary*. Retrieved November 16, 2007. an abnormal outgrowth of plant tissue usually due to insect or mite parasites or fungi and sometimes forming an important source of tannin

1. **[^](#cite_ref-Larson_1991_2-0)** Larson, K. C.; Whitham, T. G. (1991). "Manipulation of food resources by a gall-forming aphid: the physiology of sink-source interactions", *[Oecologia](/source/Oecologia)* **88**(1): 15–21. [doi](/source/Doi_(identifier)):[10.1007/BF00328398](https://doi.org/10.1007%2FBF00328398).

1. **[^](#cite_ref-3)** Weis, A. E.; Kapelinski, A. (1994). "Variable selection on *Eurosta*'s gall size. II. A path analysis of the ecological factors behind selection", *Evolution* **48**(3): 734–745. [doi](/source/Doi_(identifier)):[10.1111/j.1558-5646.1994.tb01357.x](https://doi.org/10.1111%2Fj.1558-5646.1994.tb01357.x).

1. **[^](#cite_ref-Stone_2003_4-0)** Stone, G. N.; Schonrogge, K. (2003) "The adaptive significance of insect gall morphology", *Trends in Ecology & Evolution* **18**(10): 512–522. [doi](/source/Doi_(identifier)):[10.1016/S0169-5347(03)00247-7](https://doi.org/10.1016%2FS0169-5347%2803%2900247-7).

1. **[^](#cite_ref-5)** Volovnik, S. V. (2010). "Weevils Lixinae (Coleoptera, Curculionidae) as Gall Formers", *Entomological Review*, **90**(5): 585–590. [doi](/source/Doi_(identifier)):[10.1134/S0013873810050052](https://doi.org/10.1134%2FS0013873810050052).

1. ^ [***a***](#cite_ref-Brandão‐Dias_Zhang_Pirro_Vinson_2022_6-0) [***b***](#cite_ref-Brandão‐Dias_Zhang_Pirro_Vinson_2022_6-1) Brandão-Dias, Pedro F. P.; Zhang, Yuanmeng Miles; Pirro, Stacy; Vinson, Camila C.; et al. (2022). "Describing biodiversity in the genomics era: A new species of Nearctic Cynipidae gall wasp and its genome". *Systematic Entomology*. **47** (1). Wiley: 94–112. [Bibcode](/source/Bibcode_(identifier)):[2022SysEn..47...94B](https://ui.adsabs.harvard.edu/abs/2022SysEn..47...94B). [doi](/source/Doi_(identifier)):[10.1111/syen.12521](https://doi.org/10.1111%2Fsyen.12521). [ISSN](/source/ISSN_(identifier)) [0307-6970](https://search.worldcat.org/issn/0307-6970).

1. **[^](#cite_ref-Krusberg_1963_7-0)** Krusberg, L. R. (1963). "Host Response to Nematode Infection". *Annual Review of Phytopathology*. **1** (1). Annual Reviews: 219–240. [Bibcode](/source/Bibcode_(identifier)):[1963AnRvP...1..219K](https://ui.adsabs.harvard.edu/abs/1963AnRvP...1..219K). [doi](/source/Doi_(identifier)):[10.1146/annurev.py.01.090163.001251](https://doi.org/10.1146%2Fannurev.py.01.090163.001251). [ISSN](/source/ISSN_(identifier)) [0066-4286](https://search.worldcat.org/issn/0066-4286).

1. **[^](#cite_ref-Williamson_Hussey_1996_8-0)** Williamson, V. M.; Hussey, R. S. (1996). ["Nematode pathogenesis and resistance in plants"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC161311). *The Plant Cell*. **8** (10). Oxford University Press: 1735–1745. [doi](/source/Doi_(identifier)):[10.1105/tpc.8.10.1735](https://doi.org/10.1105%2Ftpc.8.10.1735). [ISSN](/source/ISSN_(identifier)) [1040-4651](https://search.worldcat.org/issn/1040-4651). [PMC](/source/PMC_(identifier)) [161311](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC161311). [PMID](/source/PMID_(identifier)) [8914324](https://pubmed.ncbi.nlm.nih.gov/8914324).

1. **[^](#cite_ref-9)** Terrell, E. E.; Batra, L. R. "*Zizania latifolia* and *Ustilago esculenta*, a grass-fungus association", *Economic Botany* **36**(3): 274–285. [doi](/source/Doi_(identifier)):[10.1007/BF02858549](https://doi.org/10.1007%2FBF02858549).

1. **[^](#cite_ref-The_Royal_Society_1958_pp._188–206_10-0)** Thoday, D. (18 February 1958). "Modes of union and interaction between parasite and host in the Loranthaceae. III. Further observations on *Viscum* and *Korthalsella*". *Proceedings of the Royal Society of London. Series B - Biological Sciences*. **148** (931). The Royal Society: 188–206. [Bibcode](/source/Bibcode_(identifier)):[1958RSPSB.148..188T](https://ui.adsabs.harvard.edu/abs/1958RSPSB.148..188T). [doi](/source/Doi_(identifier)):[10.1098/rspb.1958.0013](https://doi.org/10.1098%2Frspb.1958.0013). [ISSN](/source/ISSN_(identifier)) [2053-9193](https://search.worldcat.org/issn/2053-9193).

1. **[^](#cite_ref-11)** Egan, Scott P.; Zhang, Linyi; Comerford, Mattheau; Hood, Glen R. (August 2018). ["Botanical parasitism of an insect by a parasitic plant"](https://doi.org/10.1016%2Fj.cub.2018.06.024). *Current Biology*. **28** (16): R863–R864. [Bibcode](/source/Bibcode_(identifier)):[2018CBio...28.R863E](https://ui.adsabs.harvard.edu/abs/2018CBio...28.R863E). [doi](/source/Doi_(identifier)):[10.1016/j.cub.2018.06.024](https://doi.org/10.1016%2Fj.cub.2018.06.024). [PMID](/source/PMID_(identifier)) [30130501](https://pubmed.ncbi.nlm.nih.gov/30130501).

1. **[^](#cite_ref-12)** Bavli, tractate Gittin:19a

1. **[^](#cite_ref-Mediterranean_Society_13-0)** Goitein, Shelomo Dov; Sanders, Paula (1967). [*A Mediterranean Society: Daily life*](https://books.google.com/books?id=UzOvJHFTTeUC). University of California Press. p. 405. [ISBN](/source/ISBN_(identifier)) [0-520-04869-5](https://en.wikipedia.org/wiki/Special:BookSources/0-520-04869-5). Retrieved 22 June 2020.

## Further reading

- Blanche, Rosalind (2012). *Life in a Gall: The Biology and Ecology of Insects that Live in Plant Galls*. Collingwood, Vic.: CSIRO Publishing. [ISBN](/source/ISBN_(identifier)) [978-0-643-10643-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-643-10643-7).

- Redfern, Margaret (2011). *Plant Galls*. London: Collins. [ISBN](/source/ISBN_(identifier)) [978-0-00-220144-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-00-220144-5).

- Russo, Ron (2007). *Field Guide to Plant Galls of California and Other Western States*. Berkeley, California: University of California Press. [ISBN](/source/ISBN_(identifier)) [978-0-520-24885-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-520-24885-4).

## External links

Wikimedia Commons has media related to [Galls](https://commons.wikimedia.org/wiki/Category:Galls).

Look up ***[gall](https://en.wiktionary.org/wiki/gall)*** or ***[gallnut](https://en.wiktionary.org/wiki/gallnut)*** in Wiktionary, the free dictionary.

- [British Plant Gall Society](http://www.britishplantgallsociety.org/)

- [A Field Guide to Plant Galls of the North East U.S.](http://www.bio.brandeis.edu/fieldbio/Plant_Galls/samplepage.html) [Archived](https://web.archive.org/web/20201112013223/http://www.bio.brandeis.edu/fieldbio/Plant_Galls/samplepage.html) 2020-11-12 at the [Wayback Machine](/source/Wayback_Machine)

- [To Be or Not To Be a Gall: The Story of Strange Growths on Plants](http://waynesword.palomar.edu/pljuly99.htm) [Archived](https://web.archive.org/web/20140321085200/http://waynesword.palomar.edu/pljuly99.htm) 2014-03-21 at the [Wayback Machine](/source/Wayback_Machine)

- [Insect Galls](http://www.bio.brandeis.edu/fieldbio/galls/galls.html) [Archived](https://web.archive.org/web/20201109220152/http://www.bio.brandeis.edu/fieldbio/galls/galls.html) 2020-11-09 at the [Wayback Machine](/source/Wayback_Machine). *Brandeis University*

- ["Common oak galls"](https://web.archive.org/web/20060913044856/http://www.uky.edu/Ag/Entomology/entfacts/trees/ef408.htm). *University of Kentucky Entomology*. Archived from [the original](http://www.uky.edu/Ag/Entomology/entfacts/trees/ef408.htm) on 2006-09-13. Retrieved 2006-09-11.

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