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Cypress aphidOn this page: Identification & Distribution Biology & Ecology: Taxonomy Life cycle Ant attendance Natural enemies Other aphids on the same host Damage & Control
Identification & Distribution:
Cinara cupressi apterae (see first picture below) are mainly orange brown to yellowish brown, with blackish markings diverging back from the thorax. There are only 4-6 hairs on the basal half of antennal segment six (cf. Cinara fresai which has 7-12 hairs in this position). In life the dorsum is dusted with pale grey wax making a pattern of rather interrupted cross-bands. The whole aphid is clothed with fine hairs. There is also a rather indistinct blackish band between the black siphuncular cones. The distal parts of the femora and the bases of the tibiae are dark brown or black (cf. Cinara tujafilina which has the femora pale, and tibiae wholly pale or dark only at apices). The body length of Cinara cupressi apterae is 1.8-3.9 mm.
The alate (see second picture above) has a dark thorax, an abdomen similar to the aptera and prominent black siphuncular cones. The micrographs below (dorsal and ventral) show that scleroites on the dorsum are very small or absent.
Cinara cupressi is found most commonly on cypress (Cupressus spp.) but also occurs on Thuja, Juniperus, Chamaecyparis and Widdringtonia. Oviparae and alate males occur in October in Europe. The cypress aphid is considered to be one of the world's 100 worst invasive alien species according to the criteria used by the international Union for the Conservation of Nature. It occurs in Europe, Asia, Africa and the Americas.
Biology & Ecology:
Populations thought to have originated in the Middle East and introduced to Africa (and also the UK) were formerly classified using multivariate analysis as a separate species, Cinara cupressivora (Watson et al., 1999). Geographical range was generally the most straightforward and accurate way to differentiate Cinara cupressi and Cinara cupressivora, with Britain as the only country where their ranges overlapped. However, recent studies by Remaudiere & Binazzi (2003) suggest the distinction may not be justified.
In temperate climates, eggs laid on cypress the previous autumn hatch in spring. At this time of year only females are present and they reproduce parthenogenetically (without mating), giving birth to live young. There are two adult forms - winged and wingless. Adults and juveniles are well camouflaged against tree bark.
Numbers build over the summer, but as cooler weather approaches in autumn, both males and females are produced. These mate and the resultant females (oviparae) produce eggs instead of live nymphs. The eggs are laid in rough areas on twigs and foliage where they overwinter. Several generations are produced per year.
In warm regions such as Africa, the aphid does not overwinter as an egg; instead, parthenogenetic reproduction continues all year. This, along with the absence of natural enemies, has allowed cypress aphid populations to increase rapidly in countries where the species has been introduced.
Ants may feed on the honeydew produced by the aphids.
They have also been observed transporting the aphids from one part of the tree to another, thus creating new areas of infestation.
Cinara cupressi is liberally coated in wax which discourages many predators. However we have found syrphid larvae consuming them (see picture below).
The pupa of a predatory syrphid surrounded by surviving Cinara cupressi is shown in the picture below.
Other aphids on same host:
Blackman & Eastop list 9 species of aphid as feeding on Cypresses (Cupressus species) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 5 as occurring in Britain (Show British list).
Damage and control
The cypress aphid can cause severe direct feeding damage resulting in dieback and sometimes death of host conifers with associated economic, environmental and aesthetic costs. The saliva they produce is phytotoxic and leads to necrosis in the phloem which subsequently results in the twig withering (see pictures below). The foliage also gets covered in honeydew and then mould which inhibits photosynthesis.
The impact on this on the plant depends on tree stress and weather factors. Cinara cupressi is also a vector of Cyprus canker (caused by the fungi Seridium cardinale & Lepteutypa cupress) which has devastated some cypress trees populations.
In Britain the main damage is limited to domestic garden hedges. However, in southern and eastern Africa, the cypress aphid killed a total of US$27.5 million worth of trees in 1991. At that time it was causing a loss in annual growth of US$9.1 million per year (Murphy et al., 1996). One tree species which is especially sensitive to feeding by the cypress aphid is Cupressus lusitanica. This species is highly favoured as a plantation species because of its rapid growth rate and excellent form. In Kenya, this species comprises around half of the country's total industrial forest plantation area. Loss of these plantations could have serious effects on Kenya's domestic wood supply. Also, Cupressus lusitanica is a key agroforestry species widely planted for wind-breaks, as a source of fuelwood and as living fences and hedges. In Malawi, Cinara cupressi damages the endangered national tree, Widdringtonia nodiflora (Ciesla 1991). In Chile affected native forest species include Austrocedrus chilensis and Fitzroya cupressoides (Montalva et al., 2010).
Chemical control, for example treatments containing pirimicarb, was initially tried against Cinara cupressi but is only practical for ornamental trees and hedges. Even then it must be done at the first sign of an attack or the damage to the phloem will already have been done. In Africa, various hymenopteran endoparasitoids of the genus Pauesia have been used for the biological control of Cinara cupressivora with varying levels of success (Kairo & Murphy 2005). Candidates include Pauesia cupressobii and Pauesia juniperorum, which have been found attacking Cinara juniperi. Similarly Pauesia juniperorum has been used in Chile. Efforts are being made to supplement the level of control with other natural enemies including predators and fungi.