GALLS
OAK
Oak Apples on English Oak are caused by larvae of gall wasp Biorhiza pallida. Eggs laid in oak buds produce spongy apple-like growths. Every 'apple' contains many chambers each enclosing a larva. These apples are not edible.
Marble Galls on English Oak
are produced by the asexual generation of a Gall wasp
Andricus kollari
on leaf buds. The galls (up to 25mm across) each contain one larva. Initially the galls are green, turning brown in autumn.
There is usually one large hole that newly developed adults emerge from after changing from the larval state. Smaller holes are often caused by inquiline insects that exploit the living space of others. Inquilines are not necessarily parasitic and it is possible they cause no harm to the host species. Marble Galls are high in tannin and were possibly introduced to Britain during the 19th century to supply the ink-making and dyeing industries with a convenient tannin source.
Cottonwool Galls are caused by gall wasp Andricus quercusramuli on English and Sessile Oak. The white hairs hide up to 20 chambers each occupied by one larva.
Rosebud Galls were originally found in the UK in 2008 at Colchester, Essex by Jerry Bowdrey, East Anglian Recorder, for The British Plant Gall Society. The galls (3-4mm across) caused by the asexual generation of gall wasp Andricus gemmeus are often found on Oak trunks in Hainault Forest during September.
Cluster Galls first appeared in the UK during the 1990s, originating from the Mediterranean. Thank you to Essex Field Club recorder, Jerry Bowdrey, for identifying this gall, caused by the sexual generation of a gall-wasp Andricus lucidus. Chair of the British Plant Gall Society, Tommy Root, thought this was a great find, having only seen this gall twice - both times at Tooting Common. The flower-like clusters, measuring up to 35mm across, are comprised of dish-shaped galls that push into each other. The galls are initially green with a shiny, waxy surface, becoming reddish-brown and hard. The asexual generation of this gall-wasp produce Hedgehog Galls.
Oyster Galls are induced by the asexual generation of gall wasp Neuroterus anthracinus. Tiny egg-shaped galls about 3mm diameter form on the midrib of oak leaves. There is a small flap of tissue sticking out each side of the base, it is important to see the flaps when identifying to avoid mixing up with similar species. The galls initially cream or green form reddish-brown spots before maturing and dropping from the leaves in autumn. Adult wasps emerge in winter and spring to lay eggs in buds which become the sexual generation.
Gooseberry Galls were first recorded in Essex during 2004, four years after being discovered in Berkshire. They form in large groups on male catkins of Turkey Oak. They are roundish with a pointed end. The galls are induced by the sexual generation of a gall wasp Andricus grossulariae. Immature galls are slightly hairy, waxy and bright green. They mature late spring becoming small, shiny and maroon coloured, before turning hard and woody. The galls have also been spotted at the base of a Lucombe Oak in Hainault Lodge after they have fallen from the tree.
Jumping Bean Galls are caused by the asexual generation of Gall Wasp Pseudoneuroterus saliens on Turkey Oak during autumn; either on young shoots, the mid-ribs or leaf petioles. Each gall (3-4mm long) is inhabited by one larva. The galls change colour from lemon yellow to red. When mature the galls fall to the ground and are sometimes seen jumping. 'Saliens' is Latin for 'jumping'. Adults emerge during spring to lay eggs on flowers which then produce Anemone galls.
Anemone Galls form on fertilised Turkey oak female flowers. They are induced by the sexual generation of a gall wasp Pseudoneuroterus saliens. Several larvae live in each gall and emerge as adults during summer. The first record of this gall in the UK was during 2004.
Common Spangle Galls appear on leaves, they are caused by the asexual generation of gall wasp
Neuroterus quercusbaccarum, the same species responsible for causing Current Galls. These disc-shaped galls are covered with tufts of reddish hairs. During autumn they fall from the leaf and the larvae overwinter in leaf litter.
Silk Button Galls are caused on the underside of Oak leaves by the agamic generation of gall wasp
Neuroterus numismalis. They are round, thick, with a deep central depression, looking similar in my opinion to miniature ring doughnuts up to 3mm across. These galls often appear in large numbers during autumn.
Knopper Galls on English Oak are caused by the asexual generation of gall wasp
Andricus quercuscalicis. The galls enclose acorns and raised considerable concern when introduced to Britain during the 1960s because it was thought that as acorns were being affected could diminish future generations of oak trees. Initially knoppers are green, sticky, and develop a reddish tinge. Once mature they become brown and woody. They drop to the ground in late summer and gall wasps usually emerge the following spring.
Striped Pea Galls are caused on Oak leaves by the asexual generation of gall wasp Cynips longiventris.
Cherry Galls are abnormal growths that appear on the underside of English Oak leaves during autumn. They are caused by the asexual generation of gall wasp Cynips quercusfolii. The galls are green, then red. Usually one per leaf but sometimes there may be more. Late in the year they are seen on fallen leaves on the forest floor.
Ramshorn Galls Andricus aries were first recorded in Britain during 1997. This gall found on English Oak has a roundish base from which 'horns' (usually 20-30mm) protrude. During summer the green gall forms from a bud which turns woody-brown as it ages.
Artichoke Gall (aka Hop Galls) that grow on English Oak are induced by the asexual generation of gall wasp Andricus foecundatrix. The galls start appearing about June. The enlarged buds grow up to 30mm in length. Only one larva lives inside each gall. The mature gall falls to the ground during August leaving the dried scales remaining on the twig.
Felt Galls are present on Holm Oak throughout the year. They are caused by the mite Aceria ilicis. Underneath an abnormal felty brown growth of hairs (erineum) forms from the leaf epidermis.
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