Gall

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Image:Crown-gall.jpg Image:Crown-gall detail.jpg

For other uses, see Gall (disambiguation).

Galls are proliferations of cell tissue in plants and can be caused by various parasites, from fungi and bacteria, to insects and mites. Galls are often very organised structures and because of this, the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite galls.

1 Creatures that induce galls

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Creatures that induce galls

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Insects

Galls induced by insects are called insect galls. Insects that induce insect galls are called gall-inducing insects. Insect galls are usually induced by the chemicals injected by the larvae or the adults when they consume part of the plants. After the galls were formed, the larvae stay inside and develop until fully grown, at which time they leave. In order to form galls, the insects must seize the time when plant cell division occurs at a high speed, and when the plant tissues are still growing, normally spring. Although insect galls can be found on a variety of parts of the plant, such as the leaves, stalks, branches, buds, roots or even flowers, gall-inducing insects are fairly particular about which tissue of the plants or what kind of plants they make galls on. They would at most make galls on plants similar to those that they usually make galls on.

Gall-inducing insects include gall wasps, gall midges, aphids, and psyllids.

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Uses

Galls are rich in resins and tannic acid and have been used in the manufacture of permanent inks and astringent ointments, in dyeing, and in tanning. A high-quality ink has long been made from the Aleppo gall, found on oaks in the Middle East; it is one of a number of galls resembling nuts and called gallnuts or nutgalls.

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