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Semiaphis dauciWaxy carrot aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionAdult apterae of Semiaphis dauci are pale blue-green with a grey head and waxy bloom. Their antennae are 0.4-0.5 times the body length with a terminal process that is 1.7-2.5 times as long as the base of antennal segment VI. The longest hair on antennal segment III is shorter than half the basal diameter of that segment. The apical rostral segment (RIV+V) is as long as or shorter than the length of the second hind tarsal segment. There are dark dorsal cross bands on tergites VIII and VIII. Hairs on the body and appendages are very short; the posterior hair on the hind trochanter rarely exceeds 20μm, and is less than 0.5 times the diameter of trochantro-femoral suture (cf. Semiaphis heraclei on many Apiaceae, including Daucus in Asia, which has that hair greater than half that diameter). The first segment of the hind tarsus has only 2 hairs (cf. Semiaphis anthrisci on Torilis in Europe, which usually has 3 hairs on the hind tarsus). There is no supracaudal process (cf. Cavariella spp., which possess a supracaudal process). The siphunculi are quite short and flangeless, only about 0.5 times the length of the cauda or less, with their apertures slanted towards mid-line. The cauda is tongue shaped, about 1.3 times as long as its basal width. The body length of adult Semiaphis dauci apterae is 1.3-2.1 mm.
Both images above by permission, copyright Dirk Baert, all rights reserved. The alate Semiaphis dauci has a green abdomen with dark dorsal cross bands on tergites VIII and VIII and marginal sclerites. Antennal segment III has 17-22 secondary rhinaria, IV has 3-6, V has 0-1. The siphunculi are strongly curved.
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.
Image above by permission, copyright Dirk Baert, all rights reserved. The most frequent host of Semiaphis dauci is wild or cultivated carrot (Daucus carota), but it is also recorded from several other genera of the Apiaceae including ground elder (Aegopodium) and alexanders (Smyrnium). On moon carrot (Seseli spp.) it occurs as a recognised subspecies, Semiaphis dauci ssp. seselii. The feeding site in spring is on the upper sides of rolled young leaves and leaflets; later in the year they may be found in the umbels. Sexuales (oviparae & alate males) usually develop in autumn, although anholocyclic populations occur in southern England. Semiaphis dauci is found in Europe, North Africa, the Middle East, Central Asia and possibly the USA. Other aphids on the same hostSemiaphis dauci has been reported from 2 Daucus species (Daucus carota, Daucus muricatus).
Semiaphis dauci has been reported from 1 Aegopodium species (Aegopodium podagraria).
Semiaphis dauci has been reported from 1 Smyrnium species (Smyrnium olustratum)
Damage and controlSemiaphis dauci is reported to cause crinkling of carrot foliage, stunting of plants, arrested growth of young shoots and accentuated rolling of leaves where the colonies take shelter (see INRA). It has also been reported causing damage to arracacha (Arracacia xanthorrhiza), a root vegetable like Daucus in the Apiaceae that is widely grown in Brazil (Ide et al., 2011). Adult plants found infested with the aphid were underdeveloped and blossoming prematurely. In seedlings the symptoms were more severe with reduction in development and death of plants. Semiaphis dauci can also transmit celery mosaic virus (CeMV).
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