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Blackcurrant aphid, Permanent currant aphidIdentification & Distribution Biology & Ecology Other aphids on the same host Damage & Control
Identification & Distribution:Aphis schneideri apterae are dark bluish green to blackish green with distinct wax powdering. The hairs on the third antennal segment are long, acute and 2.0-3.1 times the basal diameter of that segment (cf. Aphis grossulariae which has those hairs only 1.0-1.5 times the basal diameter of that segment). The dorsal abdominal sclerotic pattern of Aphis schneideri is absent or limited at most to dusky bands across tergites 6-8. The abdominal marginal tubercles are very prominent, subconical and are often present on all segments from 1-7 inclusive. Their siphunculi and legs are pale.The cauda is short and blunt. The body length of apterae is 1.7-2.3 mm.
Alate Aphis schneideri have dark marginal and postsiphuncular sclerites, bands across tergites 6-8, and sometimes small sclerites or broken bars on tergites 1-5. The siphunculi are dark in the alate, and compared to the aptera the cauda is rather more slender and less sharply tapering over the distal two thirds.
The two images below show a dorsal and ventral view of an apterous adult Aphis schneideri in alcohol. Note especially the prominent marginal tubercles.
The blackcurrant aphid does not host alternate, hence the common name 'permanent' currant aphid. It feeds on blackcurrant (Ribes nigrum) and related currants (Ribes spp.), forming dense colonies up young shoots and under the leaves. Aphis schneideri causes bunching and leaf curl and is attended by ants. Sexual forms occur in autumn. It occurs throughout much of Europe and parts of Asia.
Rakauskas (1999) studied the possibilities of hybridisation between Aphis schneideri and Aphis grossulariae under experimental conditions (see picture below, of the latter, on its summer host, Epilobium).
Oviparae of one species were confined with a male of the other species. Hybrid eggs were produced and the resultant clones expressed normal parthenogenetic reproduction, but sexual forms were not obtained. Hybrids mostly showed the host specificity of Aphis grossulariae, accepting Epilobium as a summer host. In contrast, most hybrids showed the morphological features of Aphis schneideri. About 26% of experimental hybrid clones were morphologically intermediate between the parental species.
Rakauskas (2003) then sought to find morphologically intermediate specimens of Aphis grossulariae and Aphis schneideri in field collections from 25 countries. Such specimens of presumably hybrid origin were found in 36% samples, and 31 samples originating from 11 countries had 50% or more intermediate specimens of one or both morphs.
Rakauskas & Turcinaviciene (2003) have found a yellow colour form of Aphis schneideri in Lithuania. The colour differences between yellow and green aphids of Aphis schneideri seemed to have a genetic basis. The yellow aphids were smaller, and the yellow clones did not finish their entire life cycle, thus supporting the idea of the reduced fitness of yellow mutants. There is also a possibility that the yellow colour forms of currant inhabiting species of the genus Aphis are of hybrid origin.
Aphis schneideri eggs hatch in spring and the aphids initially feed on the flower trusses.
As the colony expands, they move on to the younger stems and the tips of young shoots.
Later in the year Aphis schneideri live on the leaf undersides. Alatae are produced in June, and these disperse locally to other currant hosts. The wingless offspring of these migrants continue to breed until the autumn when sexual forms are produced. The ovipara lays eggs on the shoots, which stay there until the next spring.
Much like the host-alternating Aphis grossulariae, Aphis schneideri is often, but not always, attended by ants.
We have usually found that the species is ant attended, although there are surprisingly few references to it in the literature. Tido (2012) records that a small colony of Aphis schneideri on blackcurrant were attended by ants.
Similarly David Hubble has an excellent blog about the mutualistic relationship between ants and aphids as exemplified by Lasius niger attending Aphis schneideri on blackcurrant.
Although there are rather few records, it seems likely that the natural enemy complex of Aphis schneideri on blackcurrant will resemble that of Aphis grossulariae on gooseberry. We have found what appear to be mummies caused by Lysiphlebus fabarum in colonies of Aphis schneideri on blackcurrant (see two pictures below).
Petrovic et al. (2013) reported the invasive Lysiphlebus orientalis attacking Aphis schneideri in Serbia, and Stary et al. (2014) reported Lysiphlebus fabarum on Aphis schneideri in his review of parasitoid-aphid-plant associations in the Czech Republic.
As with Aphis grossulariae, the attending ants do not seem to protect these aphids from the attentions of Lysiphlebus parasitoids.
Other aphids on same host:Blackman & Eastop list 22 species of aphid as feeding on Blackcurrant (Ribes nigrum) worldwide, and provide formal identification keys. Of those aphid species, Baker (2015) lists 14 as occurring in Britain: Aphis fabae, Aphis grossulariae, Aphis schneideri, Aphis triglochinis, Cryptomyzus galeopsidis, Cryptomyzus galeopsidis ssp. citrinus, Cryptomyzus galeopsidis ssp. dickeri, Cryptomyzus ribis, Eriosoma ulmi, Hyperomyzus lactucae, Hyperomyzus pallidus, Hyperomyzus rhinanthi, Nasonovia ribisnigri and Rhopalosiphoninus ribesinus.
Damage and control
Mitchell et al. (2011) note that attacks on young plants can be particularly devastating.
The dense colonies of Aphis schneideri on shoot tips (see picture above) cause the characteristic damage of tight bundles of distorted leaves, which all bend down from where the leaf attaches to the petiole. These leaves remain green.
Mitchell et al. (2011) describe the main approaches to control of currant aphids. Growers in the U.K. usually apply one or more preventive or curative aphicide sprays in the spring, before and/or after blossom. Selective systemic materials are often preferred because they can control aphids inside curled leaves without direct spray interception and are less harmful to natural enemies. Use of synthetic pyrethroids is discouraged because they are not very effective against aphids and are very harmful to a wide range of natural enemies, and thus are highly disruptive of integrated pest management. However, a single spray of an aphicide in early October can be useful to control females on the undersides of leaves before they lay overwintering eggs on the bark.
Aphis schneideri has been reported as a vector of gooseberry vein banding virus (Brennan, 1996 ).