Gall
Galls (from the
. Plant galls are often highly organized structures so that the cause of the gall can often 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.[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 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.
Many gall insects remain to be described. Estimates range up to more than 210,000 species, not counting parasitoids of gall-forming insects.[6]
Cynipid wasps
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).[6] These are often restricted taxonomically to a single host species or a group of related species.
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Oak artichoke gall caused by Andricus foecundatrix
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Artichoke gall cut open to reveal wasp larva
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Knopper gall caused by Andricus quercuscalicis
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Oak gall caused by Neuroterus albipes forma laeviusculus
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Marble gall of oak caused by Andricus kollari
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Cherry oak gall caused by Cynips quercusfolii
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Cherry oak gall cut open to reveal wasp larva
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Cherry oak gall wasp adult
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pedunculate oak
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Cola-nut galls (Andricus lignicola) on pedunculate oak
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Kokkocynips rileyioak gall
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Phylloteras poculum oak galls
Non-cynipid wasps
Some wasps from other groups, such as the
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Section through young bedeguar gall showing wasp larvae and cells
Hemipteran bugs
Among the
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Developing pineapple pseudocone galls onAdelges abietis
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Pineapple gall cut open to show the woolly aphid larvae inside
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Sitka sprucecaused by Adelges abietis
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Pachypsylla celtidisumbilicus hackberry gall
Dipteran flies
Some
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Nettle gall caused by Dasineura investita (Cecidomyiidae)
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False nettle stem gall caused by gall midge Neolasioptera boehmeriae (Cecidomyiidae)
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Schizomyia impatientis (Cecidomyiidae) jewelweed flower gall
Mites
Mites, small arachnids, cause distinctive galls in plants such as the
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Lime nail galls caused by the mite Eriophyes tiliae
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.[7][8]
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JuvenileMeloidogynepenetrating a host plant
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Root-knot galls caused by the nematodeMeloidogyne
Fungi
Many
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.[9]
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Gall on coniferPucciniales)
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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.
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Crown gall on Kalanchoe infected with Agrobacterium tumefaciens
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Citrus vein enation woody gall onvector
Plants
The
Uses
Galls are rich in
Medieval
See also
- British Plant Gall Society
- Forest pathology
- List of insect galls
- Similar structures:
- Burl
- Witch's broom
References
- ^ "gall(4)", Merriam-Webster Online Dictionary, accessed 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".
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- ^ ISSN 0307-6970.
- ISSN 0066-4286.
- PMC 161311.
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- ISSN 2053-9193.
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- ^ Bavli, tractate Gittin:19a
- ISBN 0520048695. 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 978-0643106437.
- Redfern, Margaret (2011). Plant Galls. London: Collins. ISBN 978-0002201445.
- Russo, Ron (2007). Field Guide to Plant Galls of California and Other Western States. Berkeley, California: University of California Press. ISBN 978-0520248854.
External links
- British Plant Gall Society
- A Field Guide to Plant Galls of the North East U.S.
- To Be or Not To Be a Gall: The Story of Strange Growths on Plants Archived 2014-03-21 at the Wayback Machine
- Insect Galls. Brandeis University
- "Common oak galls". University of Kentucky Entomology. Archived from the original on 2006-09-13. Retrieved 2006-09-11.