Plagiotrochus quercusilicis (Fabricius, 1798)

on Quercus, agamous generation

gall

Fusiform to almost imperceptible, woody, multilocular swelling of the twigs, up to 1.5 x 3 cm in size; the individual cells measure 1×3.5 mm, parallel to the length of the twig. Often only the circular, 1 mm large exit holes (in combination with the conspicuous sexual galls) betray the gall. The development of the galls may take two or three years.

host plants

Fagaceae, narrowly monophagous

Quercus coccifera, ilex.

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on Quercus, sexual generation

Quercus coccifera, Frankrijk, dép. Aude, Narbonne, 21.v.2021 © Pierre Duhem: section through a gall

galling of the axis of a male inflorescence

Quercus coccifera; this galling of the axis of the male catkin originally was considered a distinct species viz. P. fusifex (from Houard, 1908a).

Quercus coccifera, Crete, Ardaktos, 10.iv.2017 Cor Zonneveld

Quercus ilex, Britain, Essex, Colchester, 15.v.2018 © Maria Fremlin

Quercus coccifera, Portugal, Charneca da Caparica, Mata Nacional dos Medos, x.2017 © Maria Fremlin

gall

Multilocular, eventually red swelling of the lamina, equally strongly protruding at both sides. The small leaves of Q, coccifera are almost entirely galled, leaving only the spiny leaf margins. Also the axis of the male catkins may turn into a shiny bright red sausage, with the remnants of the flowers attached to the outside.

host plants

Fagaceae, narrowly monophagous

Quercus coccifera, ilex, rotundifolia.

distribution within Europe

According to (PESI, 2018) France, Italy and the Iberian Peninsula; as the photo above demonstrates also Britain, where the species is expanding (Maria Fremlin, in litt., 2018).

synonyms

Plagiotrochus fusifex Mayr, 1882; P. f. var. ilicina Tavares, 1900; P. ilicis Lichtenstein, 1877; P. emeryi Mayr, 1882; P. lichtensteni, ilicis var. lichtensteini von Dalla Torre & Kieffer, 1910; Plagiotrochus ilicis var. abdominalis Kieffer, 1897-1901; Plagiotrochus ilicis var. nigra Kieffer, 1897-1901; Plagiotrochus ilicis var. Kiefferi Kieffer, 1897-1901.

inquilines

Saphonecrus lusitanicus.

parasitoids, predators

Aprostocetus aethiops, fusificola; Aulogymnus arsames, bicolor; Cecidostiba hilaris, ilicina; Eupelmus seculatus, urozonus; Eurytoma brunniventris; Mesopolobus lichtensteini, mediterraneus, tarsatus, tibialis, xanthocerus; Ormyrus pomaceus; Pediobius rotundatus; Sycophila binotata, flavicollis, variegata; Torymus flavipes, notatus.

references

Askew, Blasco-Zumeta & Pujade-Villar (2001a), Béguinot (2003a), Bellido, Ros-Farré & Pujade-Villar (2003a), Bellmann (2012a). Blanes-Dalmau, Caballero-López & Pujade-Villar (2017a), Bowdrey & Notton (2019a), Cerasa (2015a), Cogolludo (1921a), Dauphin & Aniotsbehere (1997a), Fremlin (2020a), Fusu (2017a), Gómez, Hernández Nieves, Garrido Torres, ao (2006a), Hellrigl (2009a), Hellrigl & Bodur (2015a), Houard (1908a), Karaca & Katılmış (2020a), Katılmış & Kıyak (2008a), Kemal & Koçak (2010a), Nieves & Askew (1988a), Nieves-Aldrey (1981a, 1984b, 2001a), Nieves-Aldrey, Gómez, Hernández Nieves & Lobo (2006a), Pellizzari (2010a), Pujade, Villemant & Andreï-Ruiz (2000a), Redfern & Shirley (2011a), Sakaltaş Ariyak & Tüzün (2014a), Salas-Remón, Llimona, Lozano ao (2015a), Shachar, Melika, Inbar & Dorchin (2018a), Tavares (1905a), Tomasi (2014a).