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Small raspberry aphidIdentification & Distribution Biology & Ecology Other species on the same host Damage & Control
Identification & Distribution:Viviparous apterae of Aphis idaei are small mottled green and yellow aphids with a rather even wax pulverulence giving an overall pale green colour. The abdominal dorsum in apterae is quite pale. Aphis idaei is characterized by the combination of long very slender dusky siphunculi and a short thick blunt cauda. The siphunculi of Aphis idaei apterae are 2.4-3.3 times as long as the cauda. In midsummer their progeny develop into dwarf apterae which are pale cream and live dispersed between the veins of the underside of the leaves. The body length of apterae is only 1.3-2.2 mm (dwarfs 0.8-0.9 mm).
Alatae (see pictures above) are similarly coloured to the spring apterae, but have dark marginal and postsiphuncular sclerites and bands across tergites 7-8. Their siphunculi are 2.1-2.7 times the length of the cauda, and the body length is 1.5-1.9 mm.
The small raspberry aphid does not host alternate. It feeds on raspberry (Rubus idaeus) causing strong leaf curl in early summer. It also occurs on loganberry. Aphis idaei considered one of the most damaging pests of raspberry canes (Gordon et al., 1997 ). Sexual forms occur in autumn with apterous males. It occurs through most of Europe, west Siberia and in New Zealand and North America.
Biology & Ecology:
Dicker (1940) describes the biology of Aphis idaei on raspberry at East Malling in Kent. The eggs are laid singly on the current year's cane, usually on the upper half, and always either at the junction of a petiole with the cane or between the axillary bud and the cane. The first young aphids can be observed in mid-March, and hatching is usually complete by early April. The fundatrices mature about a month after hatching, when the fruiting laterals have developed and the young blossom buds are free from unfolding leaves. The fundatrices and their progeny migrate from leaf to leaf and congregate in large colonies round the stalks of the cluster of fruit buds. They are constantly attended by ants. The first and second generations are apterous, but most of the third are alate. These alate viviparae first appear at the beginning of June, are most numerous a month later and disappear at the end of July or in early August. The alatae shown below were present in July.
They do not migrate to an alternate food-plant, but disperse chiefly to the young raspberry canes, where they feed singly on the lower surfaces of the leaves. Their progeny are apterous viviparae, and no other forms are produced until early October, when sexuales appear. By November, only the sexual forms are present, and these persist in diminishing numbers until the canes have lost all their leaves (about mid-December).
Borowiak-Sobkowiak (2005) described the bionomy and ecology of Aphis idaei on raspberry in Poland. Egg hatching took place at the end of March and the beginning of April. 7-8 generations in a season were observed. The highest fecundity was recorded in the fundatrix. High summer temperatures (greater than 35°C) caused high mortality, curbed development and reduced fecundity.
Other species on the same host
Blackman & Eastop list about 14 species of aphids as feeding on raspberry worldwide, and provides formal identification keys for aphids feeding on various Rubus species. Of these aphid species, Baker (2015) lists 9 as occurring in Britain: Amphorophora idaei, Aphis gossypii, Aphis idaei, Aphis ruborum, Macrosiphum euphorbiae, Macrosiphum funestum, Myzus ornatus Pemphigus rubiradicis and Sitobion fragariae.
Damage and control
Aphis idaei is a major pest of raspberry. Direct feeding by spring colonies at the tips of the young canes causes severe leaf curl. It is the vector of Raspberry leaf mottle virus (RLMV), Raspberry leaf spot virus (RLSV), Black raspberry necrosis virus (BRNV) and Rubus yellow net virus (RYNV).
Because aphid-resistant raspberry genotypes additionally show a reduced occurrence of viruses, Schliephake (2010) investigated whether the feeding behaviour of Aphis idaei differed between aphid resistant and susceptible plants. The investigations of the aphid development showed clearly that the tested cultivars differed in their suitability for aphids as host plants. But the probing and feeding behaviour of Aphis idaei, which is responsible for virus transmission, was not sufficiently different between resistant and susceptible cultivars to be the reason for virus resistance.