Gall

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

title: "Gall" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["galls"] description: "Abnormal growths especially on plants induced by parasitic insects and other organisms" topic_path: "general/galls" source: "https://en.wikipedia.org/wiki/Gall" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

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

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b9/Andricus_lignicola_-_Cola-nut_Gall.JPG" caption="[[Cola-nut gall]]s (''[[Andricus lignicola]]'') on [[pedunculate oak]], caused by a cynipid [[gall wasp]]"] ::

Galls (from the Latin galla, 'oak-apple') or cecidia (from the Greek grc, anything gushing out) are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused by various parasites, from viruses, fungi and bacteria, to other plants, insects and mites. 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

Insect galls are the highly distinctive plant structures formed by some herbivorous 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. Galls may also provide the insect with physical protection from predators.

Insect galls are usually induced by chemicals injected by the larvae 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, 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, branches, buds, roots, and even flowers and fruits. Gall-inducing insects are usually species-specific and sometimes tissue-specific on the plants they gall.

Gall-inducing insects include gall wasps, gall midges, gall flies, leaf-miner flies, aphids, scale insects, psyllids, thrips, gall moths, and weevils.

Many gall insects remain to be described. Estimates range up to more than 210,000 species, not counting parasitoids of gall-forming insects.

Cynipid wasps

Main article: Gall wasp

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

File:Andricus foecundatrix Quercus01.jpg|Oak artichoke gall caused by Andricus foecundatrix File:Andricus foecundatrix larva on Quercus robur. vrouwelijke gal met larve op zomereik.jpg|Artichoke gall cut open to reveal wasp larva File:Gallwespe bedient sich Eichel2.jpg|Knopper gall caused by Andricus quercuscalicis File:Eikengallen op mannelijke bloeiwijze.jpg|Oak gall caused by Neuroterus albipes forma laeviusculus File:Oak Gall.jpg|Marble gall of oak caused by Andricus kollari File:Andricus kollari - Capanne di Marcarolo.JPG|Cherry oak gall caused by Cynips quercusfolii File:Larve Eikengalwesp (Cynips quercusfolii).jpg|Cherry oak gall cut open to reveal wasp larva File:Cynips quercusfolii.jpg|Cherry oak gall wasp adult File:Red-Pea gall Cynips divisa on Oak.JPG|Red-pea gall (Cynips divisa) on pedunculate oak File:Kokkocynips rileyi oak gall crop.jpg|Kokkocynips rileyi oak gall File:Phylloteras poculum oak gall crop.jpg|Phylloteras poculum oak galls

Non-cynipid wasps

Some wasps from other groups, such as the Diplolepididae and the Chalcidoidea, also cause plant galls.

File:Diplolepis-rosae.jpg|Rose bedeguar gall on a wild rose, caused by Diplolepis rosae, a diplolepid wasp File:Diplolepis rosae 12 ies.jpg|Section through young bedeguar gall showing wasp larvae and cells File:Gall attack.JPG|Gall on Eucalyptus due to chalcid wasp Leptocybe invasa, India

Hemipteran bugs

Among the hemipteran bugs that cause galls are the psyllid bug Pachypsylla celtidisumbilicus, and the woolly aphid Adelges abietis, which parasitises coniferous trees such as the Sitka spruce and the Norway spruce.

File:Developing Pineapple Gall.JPG|Developing pineapple pseudocone galls on Norway spruce, caused by woolly aphid Adelges abietis File:Sacchiphantes abietis-e.jpg|Pineapple gall cut open to show the woolly aphid larvae inside File:Pineapple gall.JPG|Pineapple gall on Sitka spruce caused by Adelges abietis File:Pachypsylla celtidisumbilicus gall.jpg|Pachypsylla celtidisumbilicus hackberry gall

Dipteran flies

Some dipteran flies such as the cecidomyiid gall midges Dasineura investita and Neolasioptera boehmeriae, and some Agromyzidae leaf-miner flies cause galls.

File:Gall of Japanagromyza inferna in Centrosema virginianum L. - ZooKeys-374-045-g006.jpg|Gall of Japanagromyza inferna (Agromyzidae) in Centrosema virginianum File:Dasineura investita gall.jpg|Nettle gall caused by Dasineura investita (Cecidomyiidae) File:Neolasioptera boehmeriae crop.jpg|False nettle stem gall caused by gall midge Neolasioptera boehmeriae (Cecidomyiidae) File:Schizomyia impatientis galls.jpg|Schizomyia impatientis (Cecidomyiidae) jewelweed flower gall File:Pittosporum undulatum leaf (3128052860).jpg|Phytoliriomyza pittosporophylli (Agromyzidae) galls in leaf of Pittosporum undulatum

Mites

Mites in the family 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.

File:Eriophyes tilae tilae close up.JPG|Lime nail galls caused by the mite Eriophyes tiliae File:Gall mites on purple coneflower.jpg|Galls on purple coneflower caused by an undescribed mite species File:Poison Ivy Leaf Mite imported from iNaturalist photo 125991874 on 9 November 2023.jpg|Poison ivy leaf galls caused by Aculops rhois

Nematodes

Nematodes are microscopic worms that live in soil. Some nematodes (Meloidogyne species or root-knot nematodes) cause galls on the roots of susceptible plants. The galls are often small.

File:A juvenile root-knot nematode (Meloidogyne incognita) penetrates a tomato root - USDA-ARS.jpg|Juvenile Meloidogyne penetrating a host plant File:Nematode nodules.jpg|Root-knot galls caused by the nematode Meloidogyne

Fungi

Many rust fungi induce gall formation, including western gall rust, which infects a variety of pine trees, and cedar-apple rust. Galls are often seen in Millettia pinnata leaves and fruits. Leaf galls appear like tiny clubs; however, flower galls are globose. Exobasidium often induces spectacular galls on its hosts.

The fungus Ustilago esculenta associated with Zizania latifolia, a wild rice, produces an edible gall highly valued as a food source in the Zhejiang and Jiangsu provinces of China.

File:Gymnosporangium juniperii telial form.jpg|Gall on conifer Juniperus virginiana caused by Gymnosporangium (Pucciniales) File:Rhododendron ferrugineum b.JPG|Leaf galls on Rhododendron ferrugineum caused by fungus Exobasidium rhododendri

Bacteria and viruses

Gall-causing bacteria include Agrobacterium tumefaciens and 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 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.

File:Crown-gall detail.jpg|Crown gall on Kalanchoe infected with Agrobacterium tumefaciens File:Citrus_vein_enation_(CVEV)_on_Fortunella_japonica.jpg|Citrus vein enation woody gall on Fortunella japonica caused by a pathogen with an aphid vector

Plants

The hemiparasitic plant mistletoe forms woody structures sometimes called galls on its hosts. More complex interactions are possible; the parasitic plant Cassytha filiformis sometimes preferentially feeds on galls induced by the cynipid wasp Belonocnema treatae.

Uses

Galls are rich in resins and tannic acid and have been used widely in the manufacturing of permanent inks (such as iron gall ink) and astringent ointments, in dyeing, and in leather tanning. The Talmud records using gallnuts as part of the tanning process as well as a dye-base for ink.

Medieval Arabic literature records many uses for the gall, called عفص ar in Arabic. The Aleppo gall, found on oak trees in northern Syria, was among the most important exports from Syria during this period, with one merchant recording a shipment of galls from Suwaydiyya near Antioch fetching the high price of 4½ dinars per 100 pounds. The primary use of the galls was as a 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 and intestinal ailments.

References

References

  1. "gall(4)".
  2. Larson, K. C.; Whitham, T. G. (1991). "Manipulation of food resources by a gall-forming aphid: the physiology of sink-source interactions", ''[[Oecologia]]'' '''88'''(1): 15–21. {{doi. 10.1007/BF00328398.
  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. 10.1111/j.1558-5646.1994.tb01357.x.
  4. Stone, G. N.; Schonrogge, K. (2003) "The adaptive significance of insect gall morphology", ''Trends in Ecology & Evolution'' '''18'''(10): 512–522. {{doi. 10.1016/S0169-5347(03)00247-7.
  5. Volovnik, S. V. (2010). "Weevils Lixinae (Coleoptera, Curculionidae) as Gall Formers", ''Entomological Review'', '''90'''(5): 585–590. {{doi. 10.1134/S0013873810050052.
  6. (2022). "Describing biodiversity in the genomics era: A new species of Nearctic Cynipidae gall wasp and its genome". Wiley.
  7. Krusberg, L. R.. (1963). "Host Response to Nematode Infection". Annual Reviews.
  8. (1996). "Nematode pathogenesis and resistance in plants.". Oxford University Press.
  9. Terrell, E. E.; Batra, L. R. "''Zizania latifolia'' and ''Ustilago esculenta'', a grass-fungus association", ''Economic Botany'' '''36'''(3): 274–285. {{doi. 10.1007/BF02858549.
  10. (18 February 1958). "Modes of union and interaction between parasite and host in the Loranthaceae. III. Further observations on ''Viscum'' and ''Korthalsella''". The Royal Society.
  11. (August 2018). "Botanical parasitism of an insect by a parasitic plant". Current Biology.
  12. Bavli, tractate Gittin:19a
  13. (1967). "A Mediterranean Society: Daily life". University of California Press.

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