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Black-stem aphidOn this page: Identification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:Apterae of Cinara confinis are greenish-black (see first picture below) or dark brown (see second picture below), with a double row of blackish slightly shining speckles and small flecks of fine wax in transverse rows. The head and thoracic plates are dark brown. The antennae are pale yellowish-grey with a darkening of each segment distally. Cinara confinis tarsi are black. The tibia and femora either have dark brown annulations or are mainly black. The siphuncular cones are dark and prominent. The body length is 3.8-7.8 mm
The length of the sclerotized part of the stylet groove is greater than 1.8 mm. The length of the fifth antennal segment, including the terminal process, is clearly longer than the fourth antennal segment.
Cinara confinis feeds on the stems and twigs (rarely on the roots) of various fir (Abies) and cedar (Cedrus) species. It has a holarctic distribution and is recorded from Europe, much of Asia, North America (formerly known as Cinara grossa) and Argentina. Carter & Maslen (1982) describe it as of sporadic occurrence in Britain occurring in northern Scotland, west of Ireland and southern England.
Biology & Ecology:
Struble et al. (1976) describe the biology of Cinara confinis (under the name Cinara abieticola) in Maine, USA. Fundatrices were first found in May at the bases of buds. Resultant colonies were generally located on the trunk just below the first whorl of branches, as shown in the picture below for a colony in Sussex, UK.
Colonies disperse rapidly if disturbed. Apterous females tend to drop off but nymphs move rapidly up or down the stem and on to the branches The picture below shows a dispersing nymph moving away from a disturbed colony.
In Maine, colonies on fir trunks declined by mid June as aphids moved to root collar and roots. Winged males, oviparae and eggs can be found in October.
Binazzi & Scheurer (2009) report that Cinara confinis is optionally dependent on ant attendance. This species sometimes occurs in special earth galleries constructed by ants on the bark of fir trees (Wood-Baker, C., 1964 ). All the colonies we have found have been strongly attended by southern wood ants (Formica rufa).
On one occasion several of the colony had been parasitized despite the presence of ants. The resultant aphid mummies were blackish and are shown below left. The adult parasitoid is shown below second.
On the basis of the extraordinary number of antennal segments (Baker, pers. comm.), this parasitoid is almost certainly Pauesia grossa. This species is a parasitoid specific to Cinara confinis, but it has not been previously recorded in UK. Few predators have been observed around Cinara confinis colonies, although Struble et al. (1976) reported larvae of Metasyrphus medius in June.
Damage and control
Although Cinara confinis is still rare in Britain, it can occur in enormous numbers on large fir and cedar trees grown for their amenity value in urban areas of the USA. With large infestations, the tendency of the aphids to wander about a lot means they can cause a public nuisance - which is accentuated by the honeydew deposits, sooty moulds and abundant wasps.
The image above is of an Abies amabilis (Pacific silver fir) found infested with Cinara confinis at Bedgebury Pinetum, UK.