Plant Parasites of Europe

leafminers, galls and fungi

gallers on Larix

Dichotomous table for gallers on Larix

by Hans Roskam

1a On tips of main and side shoots, on male flower buds or on needles => 5

1b On stem parts, branches or twigs => 2

1c Orange-red larvae develop in cones of L. decidua, x polonica: Resseliella skuhravyorum

2a On older stem parts or on thicker branches => 4

2b On thinner twigs => 3

3a Oblong or often nodule-shaped, cherry- to hazelnut-size swelling on younger stems or twigs, often at the base of a branching and ± covered with a grey resin blister. L. decidua: Cydia zebeana

3b Elongate resinous swelling about twice stem width at its widest; soft and spongy, becoming hard and woody after adult emerges in May, June. Containing caterpillar for 22 months from June onwards, pupa April, May second year. L. decidua: Cydia millenniana

3c Bark of twigs with small swellings, pubescent inside. L. decidua: Trisetacus laricis

4a Long club-shaped swelling on stems and branches, bearing a bush of mistletoe. L. kaempferi: Viscum album

4b Scurfy, cracked, ± dark coloured, 15–40 cm long patches of bark ± deeply depressed, rimmed at margin with resin reacting with cancers on at first sometimes swollen parts of branches, occasionally also on the stems. Infections starting from 2–4 year old branches. L. decidua: Lachnellula willkommii

5a On the tips or short- and long shoots, also on male flower bud => 7

5b Needles slightly thickened, discoloured, almost bent over at right angles; an aphid present at the bending point => 6

6a Aphid dark brown to black, naked or covered with wax flakes. L. decidua, x eurolepis, gmelinii, kaempferi, laricina, lyallii, sibirica: Adelges laricis

6b Aphid yellow-green to dark green, without wax cover, only slightly frosted. L. decidua, x eurolepis, kaempferi, sibirica: Sacchiphantes viridis

6c To the same species group belongs the anholocyclic (only asexual females known), only on Larix spp. living: Sacchiphantes segregis

7a Tips of previous year’s short shoots swollen ± hemispherically. Galls up to pea-size, also the male flower buds occasionally transformed to similar, more or less egg-shaped, usually larger galls. Galls to August with brown scales, covered later on at first with bright fluid, then white crumbly resin, driving neighbouring needles widely apart, star-like. Containing a single brick-red larva in the upper part of the gall. L. decidua, occidentalis: Dasineura kellneri

7b Similar, globular to oblong-egg-shaped brown galls; often also on terminal buds of long shoots; in contrast with the previous midge galls, which may also be present, always dry, lacking a resin cover. L. decidua: Trisetacus laricis

Last modified 2.v.2020