Plant Parasites of Europe

leafminers, galls and fungi

genus Thesium

organ parasitic mode stage note taxonomic group parasite
leaf hidden Epermeniidae Epermenia scurella
leaf hidden Tortricidae Celypha cespitana
leaf miner younger larva Tortricidae Cnephasia asseclana
leaf hidden older larva Tortricidae Cnephasia asseclana
leaf leaf spot Capnodiales Cylindrospora thesii
root vagrant Cydnidae Canthophorus melanopterus
leaf vagrant Cydnidae Canthophorus dubius
leaf vagrant Cydnidae Canthophorus impressus
leaf vagrant Erebidae Diacrisia sannio
leaf hidden Tortricidae Clepsis rogana
leaf miner Epermeniidae Epermenia insecurella
leaf vagrant Aphididae Macrosiphum albertinae
root collar vagrant Aphididae Aphis thesii
flower gall Eriophyidae Aceria anthonoma
leaf down Erysiphales Erysiphe thesii
leaf down Peronosporales Peronospora thesii
leaf miner Agromyzidae Liriomyza thesii
leaf miner Epermeniidae Epermenia pontificella
leaf miner Epermeniidae Ochromolopis ictella
leaf pustule aecia uredinia telia Pucciniales Puccinia mougeotii
leaf pustule aecia uredinia telia Pucciniales Puccinia passerinii
leaf pustule aecia uredinia telia Pucciniales Puccinia thesii
stem gall Asterolecaniidae Planchonia arabidis


the part of the plant that most conspicuously is hit by the parasite

all buds: both flower buds and leaf buds
flower: also inflorescence
leaf: also needle, phyllodium, petiole
leaf bud: also unfolding young leaf
fruit: also seed
root: also root stock, runners
root collar: also the lowest part of the stem
stem: also culm, the lower part of the peduncle, in grasses also leaf sheath
systemic: the entire above-ground plant.


borer: larva living internally, almost no outwards signs
down: 0.5-2 mm high fungal down
film: very thin cover of fungal tussue
gall: swelling and/or malformation
grazer: feeding at the outside of the plant
leaf spot: discoloured, often ± necrotic, generally not galled, sign of a fungus infection
miner-borer: larve initially makes a mine, lives as a borer later
pustule: plug of fungal tissue, generally brown-black and < 2 mm
stripe: longitudinal line of fungal tissue in a grass leaf
vagrant: (aphids, mites) living freely on the plant, at higher densitiy causing malformations.


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The host plant spectre of a parasite is rarely known exhaustively; this applies in particular at the species level. It is advisable therefore to check at least also the list of all parasites of this genus.


Last modified 4.ii.2023