Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Dryopteris

Dichotomous table for gallers on Dryopteris

(incl. Lastrea, Nephrodium)

by Hans Roskam

1a On the leaflet leaf blades => 2

1b Tip of frond shortened, spirally rolled upward, including the crowded, only slightly changed side leaflets making a conspicuous nest with a white larva on the ± thickened midrib. D. carthusiana, cristata, dilatata, filix-mas: Chirosia betuleti

2a Leaf blade on underside sometimes ± fleshy because of enlarging of mesophyll- or epidermis cells; occasionally swollen, almost blister-like yellowish-brownish discoloured; fungus galls => 4

2b Malformations caused by animal parasites => 3

3a Leaflets with small pustules which contain eggs, mainly situated at margin, rapidly becoming necrotic after larval emergence. “Procecidia”, oviposition scars, not true galls. D. filix-mas: Aneugmenus coronatus

3b Margin of leaflets folded, discoloured, slightly thickened. Thelypteris palustris: Undescribed gall midge

3c Rounded swelling on rachis, about 2 mm long; containing a pale green caterpillar which bites a hole and ejects froth that covers the gall. Dryopteris spp.: Blasticotoma filiceti

4a On D. campyloptera and relatives

I Mycelium intercellular. Causes ± fleshy localised swellings in tissues of thickened leaflets. D. carthusiana, dilatata: Taphrina filicina

II Mycelium only below cuticule

a Often distinctly protruding galls on leaflets, up to 5 mm broad, ± fleshy. D. carthusiana, dilatata, “rigida var. australis”, villarii: Taphrina fusca

b Up to 5 mm long galls on leaf blade. D. carthusiana, dilatata, filix-mas: Taphrina athyrii

4b On D. affinis, borreri, carthusiana, filix-mas. Small, up to 5 mm long, often many per leaf blade, ± fleshy swollen, yellow-greenish to brownish galls: Taphrina vestergrenii

Last modified 17.xi.2023