Plantparasieten van Europa

bladmineerders, gallen en schimmels

gallers on Secale

Dichotomous table for gallers on Secale

by Hans Roskam

1a On above-ground parts => 4

1b On roots => 2

2a Roots with distinctly protruding galls => 3

2b Roots externally not noticeably changed. Later on often with many cysts, about poppy-seed size, at first white, then dark brown. Roots with giant cells inside. S. cereale: Heterodera avenae

3a Roots with many small, ± spindle-shaped swellings, about 1–6 mm long and 0.5–5 mm broad, crooked or screw-shaped, bent. S. cereale: Subanguina radicicola

3b Galls spindle-shaped, of similar size, but not screw-like, curved. S. cereale: Meloidogyne hapla

4a On spikes, florets or fruits => 15

4b On vegetative parts => 5

5a On leaves or culms of already ± developed shoots => 10

5b On young plants or on plants that are severely stunted by the infestation => 6

6a Central leaves of ± swollen shoots diseased and easily pulled out before dying off. On winter grain after a cold winter, often not before early spring, conspicuous infestation is distinguished by its excessive leafiness, which later develops further if not also infected. Pattern of damage of various inducers rather similar => 7

6b Basal parts of shoots strongly thickened, with elongate onion-like swelling. Plants excessively leafy; almost cushion-like shape; new shoots almost similarly infected. Leaf blades, especially of the inner leaves, ± ruffled and spirally twisted; at first dark green, then prematurely yellowing. S. cereale: Ditylenchus dipsaci

7 Malformations caused by ± cylindrical fly maggots with buccal hooks, which are at least 4 mm long when fully grown. Central leaves soon yellowing; at base ± disintegrated => 8

7b Young shoots of winter- and summer grain at base with several larvae of puparia; sometimes, if many present, slightly swollen. Leaf sheaths closely gathered together. Leaf blades often erect, often dark green, shorter and broader, as in healthy plants. Inner leaves later on withering, without conspicuous yellowing. Shoots developing further above the lower node sometimes slightly swollen and cracked. Spikes etiolated, sessile. Underneath the sheaths are several yellowish-white larvae, about 3 mm long, lacking buccal hooks, but with bifid sternal spatula; terminally conically narrowed, also with two narrowing papillae. Puparia brown, flax seed-like. S. cereale: Mayetiola destructor

8a Damage on summer as well as on winter cereals => 9

8b Damage on winter cereals only. Inner shoots in spring soft, with brown puparium at feeding site. Delia coarctata

9a Infected shoots severely stunted and ± swollen. Mature larvae about 4 mm long, yellowish-white; at the narrowed terminal part with 2 wart-like, flattened appendages, with a shallow indentation in between. S. cereale: Oscinella frit

9b With similar biology, also on rye, is the closely related Oscinella pusilla

9c Similar malformations. Mature larvae about 7 mm long, yellowish-white. Anal segment almost hemispherical to rotund-oval with 2 flattened appendages, leaving a flat, wide depression in between. S. cereale: Chlorops pumilionis

10a Malformations on leaf sheaths or culms caused by aphids or fungi => 14

10b Galls caused by apodous larvae developing inside culms or between culm and leaf sheath => 11

11a Larvae lacking sclerotised mouthparts, living on shoots between culm and leaf sheath => 12

11b Larvae in a furrow situated below the spike, in shortened and swollen internodes, protruding into younger culm parts. Spikes ± etiolated, often remaining in the occasionally partially spreading sheath of the upper leaf. Containing a single maggot up to 7 (9) mm long, with buccal hooks. S. cereale: Chlorops pumilionis

12a Culm slightly swollen at infestation site or with ± distinct depression. Larvae 3–4 mm long, yellowish-white or orange-coloured => 13

12b Leaf sheath above the upper internode, more rarely the penultimate internode, slightly inflated; several, elongated, rimmed, saddle-shaped depressions on culm, up to 10 mm long, each containing a single 3–5 mm brick red larva. S. cereale: Haplodiplosis marginata

13a Culm above the first, more rarely the second node, with one or two expanded, black-walled, oblong, slight depressions, each containing a single orange-yellow to brick red larva. S. cereale: Hybolasioptera fasciata

13b Culm stunted; sometimes, if many larvae or puparia present, slightly swollen inside the sometimes weakly swollen leaf sheath immediately above the first or second node. Containing one to several yellowish-white larvae or flax seed-like puparia. S. cereale: Mayetiola destructor

14a Upper leaves disfigured; sheath sometimes slightly swollen; leaf blade ± twisted. The only partially developing spikes are variously disfigured. S. cereale: Sitobion avenae

14b Occasionally causing similar malformations. S. cereale: Rhopalosiphum padi

14c Leaves, sheaths and culms with long, 1–1.5 mm broad stripes of smut, slightly protruding, at first lead-grey, then breaking open and releasing black-brown spores. S. cereale, montanum, strictum: Urocystis occulta

15a Malformations mainly of ovaries or fruits, parasites develop inside => 16

15b Malformations of various floral parts or complete spikes caused by animal parasites living on the host. Inducer unknown

16a The soon disfigured ovaries are filled with compact masses of dark smut spores => 17

16b Spikelets not spreading; diseased grains much smaller than normal ones ± rotund- to oblong-oval, 2–5 mm long, 1–2.5 mm broad, dark coloured, thick-walled, pale coloured inside and filled with many eelworms. Galls dropping off prematurely. S. cereale: Anguina tritici

17a Diseased plants not conspicuously shortened => 18

17b Infected plants grow only to half the normal length. Infestation often of all florets, with shortened ovaries usually developing into ± oval variable smut bodies and containing many reticulate spores, often enveloped by slime. S. cereale: Tilletia controversa

18a Smut grains much smaller than normal, egg-shaped to cylindrical, foul-smelling when fresh, usually all florets of a spike infected. Containing brown-black spores that later form a dusty powder. S. cereale: Tilletia secalis

18b Spikes often only partially infected, usually the lower or middle part. Glumes not spreading. Brown-black, later on dusty smut sori in the ovaries that are destroyed early in development, also in the lower part of glumes. S. cereale: Ustilago nuda f. sp. tritici

Laatste bewerking 14.iv.2020