Galls or cecidia 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 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.
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
Taphrina is a fungal genus within the Ascomycota that causes leaf and catkin curl diseases and witch's brooms of certain flowering plants. One of the more commonly observed species causes peach leaf curl. Taphrina typically grow as yeasts during one phase of their life cycles, then infect plant tissues in which typical hyphae are formed, and ultimately they form a naked layer of asci on the deformed, often brightly pigmented surfaces of their hosts. No discrete fruit body is formed outside of the gall-like or blister-like tissues of the hosts. The asci form a layer lacking paraphyses, and they lack croziers. The ascospores frequently bud into multiple yeast cells within the asci. Phylogenetically, Taphrina is a member of a basal group within the Ascomycota, and type genus for the subphylum Taphrinomycotina, the class Taphrinomycetes, and order Taphrinales.
Andricus quercuscalicis is a gall wasp species inducing knopper galls.
Andricus foecundatrix is a parthenogenetic gall wasp which lays a single egg within a leaf bud, using its ovipositor, to produce a gall known as an oak artichoke gall, oak hop gall, larch-cone gall or hop strobile The gall develops as a chemically induced distortion of leaf axillary or terminal buds on pedunculate oak or sessile oak trees. The larva lives inside a smaller hard casing inside the artichoke and this is released in autumn. The asexual wasp emerges in spring and lays her eggs in the oak catkins. These develop into small oval galls which produce the sexual generation of wasps. A yew artichoke gall caused by the fly Taxomyia taxi also exists, but is unrelated to the oak-borne species. Previous names or synonyms for the species A. fecundator are A. fecundatrix, A. pilosus, A. foecundatrix, A. gemmarum, A. gemmae, A. gemmaequercus, A. gemmaecinaraeformis and A. quercusgemmae.
Taphrina pruni is a fungal plant pathogen of blackthorn that causes the pocket or bladder plum gall, a chemically induced distortion of the fruit (sloes), producing swollen on one side, otherwise deformed and flattened fruit gall without a stone. The twigs on infected plants may also be deformed with small strap-shaped leaves.
Taphrina padi is a fungal plant pathogen that induces the form of pocket plum gall that occurs on bird cherry. The gall is a chemically induced distortion of the fruits, which are swollen, hollow, curved and greatly elongated, without a seed or stone, but retaining the style. The twigs on infected plants may also be deformed with small strap-shaped leaves.
Andricus grossulariae is a gall wasp species inducing agamic acorn cup galls on oak tree acorn cups and sexual phase galls on catkins. Synonyms include Andricus fructuum, Andricus gemellus, Andricus intermedius, Andricus mayri and Cynips panteli.
Puccinia poarum, a species of fungus, known as the coltsfoot gall rust, or meadow grass rust, is a plant pathogen. This fungal parasite forms a yellow to orange gall, 1–2 cm in diameter, on the underside of leaves of coltsfoot. It also infects but does not gall grasses of the family Poaceae. P. poarum is a genetically diverse species that has been reported on at least seventy plant hosts. It was originally found on Poa fertilis and Poa nemoralis in Denmark in 1877.
The pineapple gall adelgid is a species of conifer-feeding insect that forms pineapple-shaped plant galls on its host species, commonly Norway and Sitka spruce. The adelgids are pear-shaped, soft-bodied green insects with long antennae, closely related to the aphid. Adelges lays up to one hundred eggs at a time, one on each needle. Adelges abietis is one of the most common species; synonyms are A. gallarum-abietis, Chermes abietis and Sacciphantes abietis.
Eriophyes inangulis is a mite that forms the alder vein angle gall. It develops in a chemically induced gall; a sub-spherical distortion rising up from the upper surface of the leaves of alder trees Alnus glutinosa along the midrib. Synonyms are Eriophyes laevis inangulis, Phytoptus laevis, and Cephaloneon pustulatum.
Andricus aries is a species of gall-forming wasps, in the genus Andricus. The species was named by the French entomologist Joseph-Étienne Giraud, in 1859. It is commonly found in eastern Europe and during the 21st century has spread to western Europe.
Dorytomus taeniatus is a species of weevil native to Europe. It was first described by Johann Christian Fabricius in 1781. The larvae cause a small growth on the catkins of willows.
Rabdophaga salicis is a gall midge which forms galls on sallows. It was first described by Franz von Paula Schrank in 1803.
Euura vesicator is a species of sawfly belonging to the family Tenthredinidae. The larvae feed internally in a gall on the leaves of purple willow and its hybrids. It was first described by Johann Jacob Bremi-Wolf in 1849.
Acalitus brevitarsus is an eriophyid mite which induces domed, blister like swellings, known as galls, on some species of alder.
Andricus curvator is a gall wasp which forms chemically induced leaf galls on oak trees and has both agamic and sexual generations. Agamic and sexual generations usually form two distinct galls on oak trees, but in the case of A. curvator there are six galls; the sexual generation usually on the leaf, occasionally in a twig or catkin, and the agamic generation in a bud. The wasp was first described by Theodor Hartig, a German biologist, in 1840 and is found in most of Europe.
Eriophyes laevis is a gall mite which makes small, pimple-like galls on the leaves of alder. The mite was first described by the Austrian zoologist, Alfred Nalepa in 1889 and is found in Europe and North America.
Taphrina tosquinetii is a fungal plant pathogen that causes large blisters on both surfaces of the leaves of alder.
Taphrina betulina is a fungal plant pathogen that causes the gall, witches broom, which is a chemical infection of birch buds or the developing shoots, leading to a proliferation of growth. It was first described by Emil Rostrup in 1883 and is found in Europe, New Zealand and North America.
