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Grapevine aphidOn this page: Identification & Distribution Biology & Ecology Life Cycle Natural enemies Other aphids on the same host Damage & Control
Identification & Distribution
Adult apterae of Aphis illinoisensis are quite shiny, varying in colour from reddish brown to almost black (see first two pictures below). The antennal tubercles are weakly developed. Antennal segments III, IV and V are dark at their apices. The antennae are 0.7-0.9 times as long as the body, with the terminal process 1.1-4.0 times the length of the base of antennal segment VI. The apical rostral segment (RIV+V) has 2 accessory hairs. The fore-legs have the femora and mid-tibiae pale, but the mid-legs are mainly dark, and the hind tibiae are wholly black (cf. Aphis fabae, Aphis gossypii & Aphis craccivora, which all have the hind tibiae mainly pale with black apices). Their siphunculi are black, curved outwards and quite long, approximately equal in length to the terminal process of antennal segment VI. The cauda is deep brown, distinctly constricted in the middle and is much longer than its basal width (cf. Aphis folsomii, which has a short and broad cauda, about as long as its basal width). The body length of adult apterae is 1.6-2.1 mm. Immature Aphis illinoisensis (see second picture below) are reddish brown with dark siphunculi.
The alate Aphis illinoiensis (see third picture above) is similar to the aptera but with all antennal segments equally pigmented, and 5 to 10 secondary rhinaria on antennal segment III. The pterostigma is dark.
Image above copyright David Urry under a Creative Commons Attribution License.
In North America Aphis illinoisensis has a sexual phase on its primary host, blackhaw (Viburnum prunifolium), where it overwinters in the egg stage. In spring/early summer Aphis illinoisensis host alternates to members of the grape family (Vitaceae) such as the fox grape (Vitis labrusca), common grape (Vitis vinifera) and virginia creeper (Parthenocissus quinquefolia). On grapevines it feeds on the lower surface of leaves and on tendrils. The grapevine aphid is native to the Americas being found widely in the USA, central and South America, and locally in Canada. It was introduced into Turkey and the Mediterranean region, where it is now invasive. Ben Halima-Kamel & Mdellel (2010) reported the first finding of Aphis illinoisensis in Tunisia, and Hidalgo et al. (2011) reported the first finding of the species in Spain. It has also been recorded in Greece, Montenegro, Cyprus, Malta, Israel, Egypt, Algeria, and Libya, as well as in Saudi Arabia. No sexual forms have been found outside of America, so in the areas invaded it is assumed to reproduce parthenogenetically throughout the year.
Biology & Ecology
Baker (1917) gives a full account of the life cycle of Aphis illinoisensis in Virginia, USA. Their eggs are 'polished black' and are laid upon the twigs of Viburnum prunifolium. They are usually placed most thickly around the buds, although when the plants are heavily infested they may be distributed more evenly over the twigs. The eggs sometimes hatch during quite cold weather in the third week in March, but the insects produced from these first-hatched eggs may be killed by frosts. Hatching continues until the early part of April.
On hatching the young aphid (fundatrices) seek out the buds and begin feeding. Here they remain until the buds open. When the flowers begin to open it is not uncommon to find the aphids crowded down into the flower clusters. They feed upon the stems of the individual blossoms, and when the petals begin to show the presence of the aphids is often not noticeable. They also, however, feed upon the twigs and somewhat upon the leaves. The spring migrants, which migrate to the secondary hosts, begin to appear in the second generation, although their number is not abundant until the third generation, and their production then gradually decreases for several generations. Thus the spring migration extends over a considerable period, but it is at its height during the first week in May.
The spring migrants fly to wild grapes and vineyard grapes. and are capable of rather extended flight. On the new hosts they produce both wingless and winged forms. The summer wingless forms occur very abundantly throughout the summer. They reproduce very quickly during the early summer, so that seven generations have often reached maturity by mid summer. The wingless forms reach maturity a day or two before the winged forms of the same generation. As a result, upon grape, many more wingless than winged generations are produced. The apterae vary considerably in size and color, sometimes being a distinct brown, while other specimens are deep black. They also vary considerably in size, the darker, smaller individuals occurring later in the summer. The number of young produced daily ranges from 6 to 10, and the insects live for three weeks or more. The summer wingless and winged forms do considerable damage to the vines in some sections. They attack the growing clusters, sometimes thickly covering them, and their feeding damage causes fruit stems to wither and berries to drop.
Image above copyright Stan Gilliam under a Creative Commons Attribution License.
Winged forms are produced in every generation from the second onwards. These alates show the same variations as the wingless forms, some specimens being large and light brown, while others are very small and black. The small dark forms occur during the hottest summer months, while the large paler forms are usually met earlier in the spring. The winged forms produce an average of six young a day.
The fall migrants are produced on grape plants during the early part of October and are found upon the viburnum depositing young oviparae during the second week in that month. They are somewhat different in general appearance from the viviparae, being lighter and smaller. The males are produced a little later than the fall migrants, but can be found flying at the same time and may be found on viburnum in company with the fall migrants. Thus they are on the trees in many cases before the oviparae are mature. They remain feeding upon the leaves until such time as copulation is possible. The oviparous female is a small, dark reddish aphid, produced during the early part of October on the viburnum. It feeds upon the twigs and may be found until frost kills all the insects. Each ovipara lays three to six eggs close about the buds or occasionally scattered along the twigs.
Moraiti et al. (2011) determined the thermal requirements for development of the invasive Aphis illinoisensis and assessed its performance on six grapevine cultivars of economic importance in Greece. Their developmental rate model confirmed that prevailing climatic conditions throughout the spring period in the Mediterranean regions in general, and in particular in Greece, are favourable for the grapevine aphid development. In addition, all the examined grapevine cultivars were found to be suitable host-plants. The authors noted that a priority for future research in countries where the grapevine aphid is invasive is to identify which host ensures the aphids survival through winter when grapevines loose their leaves - it has not yet been found on any Viburnum species in Europe.
Little seems to have been written about the natural enemies of the grapevine aphid. Pfeiffer & Schulz (1986) note that some grapevines are of sufficient vigour to tolerate some attack by these aphids, partly because the aphids are attacked by ladybug (coccinellid) adults and their larvae as well as by lacewing larvae. The image below showing the white egg of a syrphid fly in mid-picture reveals that syrphid larvae also predate Aphis illinoisensis.
Image above copyright Stan Gilliam under a Creative Commons Attribution License.
Havelka et al. (2011) review the situation regarding the parasitoids that attack Aphis illinoisensis on grapes in the Mediterranean area. Parasitoids of Aphis illinoisensis were only occasionally found: Aphidius matricariae in Cyprus, Turkey & Greece; Aphidius colemani in Libya; and Lysiphlebus testaceipes in Algeria. Aphidius colemani and Lysiphlebus testaceipes were thought the most promising biocontrol agents. It is suggested that Aphis illinoisensis is likely to expand further to all the grape-growing areas of the Mediterranean and even those of South-Eastern and Central Europe. This will be by a process of natural dispersal of winged alatae over both short and long range distances.
El-Gantiry et al. (2012) record Aphis illinoisensis on grapes from Egypt for the first time, and also record the parasitoids and hyperparasitoids associated with the aphid species. The parasitoids found were Aphidius colemani, Diaretiella rapae and Aphelinus albipodus; the hyperparasitoid was an Alloxysta species.
Other aphids on the same host
Aphis illinoisensis has been recorded from just 1 species of Viburnum, blackhaw (Viburnum prunifolium).
Blackman & Eastop list 3 species of aphid as feeding on Viburnum prunifolium worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 2 as occurring in Britain (Show British list).
Aphis illinoisensis has been recorded from 6 species of vine (Vitis), (Vitis bicolor, Vitis cordifolia, Vitis labrusca, Vitis tiliaefolia, Vitis vinifera, Vitis vulpina). Plus 3 other Vitaceae (Cissus microcarpa, Cissus verticillata, Parthenocissus quinquefolia).
Blackman & Eastop list 16 species of aphid as feeding on Vitis vinifera worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 9 as occurring in Britain (Show British list).
Damage and control
As we noted above, grapevine aphids have been reported to do considerable damage to the vines in some areas, with the feeding of the insects causing the berries to drop and the fruit stems to wither. McGrew & Steel (1979) say that Aphis illinoisensis is most likely to appear in dry weather, and often disappears almost completely after heavy rain. They recommend spraying with parathion or malathion if the aphids appear (but note these chemicals are banned or severely restricted in Europe). Organic methods of control include encouraging natural predators and parasitoids, and spraying the vines with 'homemade pesticide' - made by mixing one teaspoon of liquid dish-washing soap with one cup of vegetable oil, shaking it form an emulsion and then adding one quart of water.