Dichotomous table for gallers on Daucus

by Hans Roskam

1a On above-ground parts => 3

1b On root or root collar => 2

2a Side roots with nodular swellings, a few mm long, partially bearing adventitious roots. D. carota, sativus: Meloidogyne hapla

= A host-specific cyst eelworm, Heterodera carotae with lemon-shaped white or brown cysts on Daucus has been recorded

= Small solid swellings, often curved or twisted, at the tips of side roots, either the needle eelworm Longidorus sp. or dagger eelworm Xiphinema sp. Both are important vectors of viruses

2b The ± green root head thickened, torn open, later on dark-brown. Stalks of leaf tuft spongy, swollen at base, pale. Stem sometimes twisted and undulate with ± equally distributed, rugose pale-green, bulges on surface. D. carota: Ditylenchus dipsaci

3a On inflorescences, flowers and fruits => 13

3b On leaves and stems => 4

4a Large parts of leaves and often several whole leaves curled => 7

4b Leaves or stems with locally wart- or bulge-shaped swellings. Fungus galls => 5

5a Galls remain closed, compact => 6

5b Bulges on petioles, -midrib or on the tips of leaf blades, elongate spindle- to irregular cushion-shaped, ± yellowish to reddish, bearing aecia and spermogonia. D. carota & subsp. maximus, muricatus: Uromyces lineolatus

6a Galls smaller than 1 mm, wart-shaped, inside a ± golden-yellow translucent fungus containing nutritive cells. D. carota: Synchytrium aureum

6b Bulges compact, vitreous, pale green, glabrous, spindle-shaped, only a few mm or up to 15 mm long, depending on infected organ. Many spores close to vascular bundle. D. carota: Protomyces macrosporus

7a Various malformations caused by aphids; usually not species-specific => 9

7b Malformations caused by psyllids or cercopids => 8

8a Leaf midrib and side stems curved, deflected, forming a loose nest of ± curled leaflets. Usually only a few leaves disfigured. D. carota & subsp. sativus: Philaenus spumarius

8b Leaf tip downwardly deflected, upwardly ± swollen, tuberculate, not discoloured. Froth-covered nymphs usually on many strongly curled and stunted leaves. D. carota & subsp. sativus: Trioza apicalis

9a phids green in various gradations => 10

9b Aphids black. Leaf blades weakly curled and deflected. D. carota & subsp. sativus: Aphis fabae

10a Siphunculi distinctly longer than cauda => 11

10b Siphunculi very short on pale green, slightly powdered aphid. Rosette leaves usually strongly curled and densely converging, nest-like, sometimes partially reddened. D. carota & subsp. maximus + sativus: Semiaphis dauci

11a Siphunculi and cauda dark. Antennae as long as half the body length or longer => 12

11b Siphunculi and cauda in wingless aphids pale green translucent. Antennae shorter than half the body length. Aphid pale green, wax absent, distinguished by a finger-shaped tubercle above the cauda. Malformation of leaf much looser than in previous species; slightly discoloured. D. carota & subspp. maximus + sativus: Cavariella aegopodii

12a Aphid up to 2 mm long, yellowish- or greenish-white, posterior with black transverse ligatures. Plant severely stunted, partially with basally inserted severely disfigured inflorescences over all parts. Leaves strongly curled. D. carota & subsp. sativus: Dysaphis crataegi

12b Aphid about 2 mm long, greenish, often blackish-brown. Antennae exceeding the middle of body, but sometimes only a third of body length. Siphunculi distinctly club-shaped, black, about as long as the dark cauda. Usually on ± curled to the stem attached leaves as well as on inflorescence. D. carota & subsp. sativus: Hyadaphis passerinii

13a Complete or partial malformation of inflorescence => 14

13b Fruits swollen, bladder-like, protruding above the umbel. Wall thickened, usually glabrous, the outside often violet-coloured. Containing 1 (‒ 3) orange-red larvae. D. carota & subsp sativus: Kiefferia pericarpiicola

= From similar fruit galls on several umbellifers has been reared Amerapha gracilis, an inquiline of Kiefferia. Another, very rare, inquiline is Trotteria umbelliferarum.

14a Malformations involving many parts of inflorescence => 15

14b Centre of stalk of (partial) umbel swollen, club-shaped to globular. Galls single or multi-chambered; wall tough, covered with whitish-grey mycelium inside. Each chamber contains a red larva. D. carota & subsp. sativus: Lasioptera carophila

15a Inflorescence disfigured by aphids in a very irregular manner. Stalks of partial umbels ± stunted; flowers stunted; developed petals sometimes ± greened or reddened D. carota & subspp. maximus + sativus: Semiaphis dauci

15b Inflorescence usually less stunted; flowers leafy, partially developing new umbels. D. carota & subsp. sativus: Aceria carvi

mod 21.iii.2020