Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Greater black spruce bark aphidIdentification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:Apterae of Cinara piceae are uniformly jet black and are often described as "resembling the texture and shape of old droplets of tar". The anterior portion is more shiny. The spiracular openings are in a series of lateral depressions giving the abdomen a crenated appearance. The siphuncular cones are rather small with the sclerotized area usually no wider than twice the diameter of the rim. The coxae and tarsi are black. The hind femora are reddish brown and black distally. The body length of Cinara piceae is 4.5-6.7 mm.
Guest image (above-right), Copyright Ian Dawson, all rights reserved.
The alate (above right and below left) is similar in colouration to aptera. It is characterised by having 11-16 rather large secondary rhinaria on the third antennal segment (see picture below right).
The oviparous female (not pictured) is dark yellowish grey with a large pericaudal wax ring present. The apterous male is small (around 3.5 mm), more elongate than other forms and is dark bluish grey with sclerotized areas shining black.
Cinara piceae forms large colonies in spring on the undersides of older branches and on trunks of Spruce (Picea spp.). Numerous alatae are produced in May-June. The oviparae appear in September-October, move to the current year's growth and lay wax-dusted eggs on needles. They often move to ground level or the roots in summer. They are found throughout Europe and in the Far East, and may vary greatly in abundance from year to year.
Biology & Ecology:
As indicated above, Blackman & Eastop (1994) suggest that Cinara piceae may move from the undersides of older branches and trunks in spring to ground level or roots in summer. However, Völkl & Novak (1997) state they do not change feeding site through the year. The only colony we have found (shown below) was thriving in June, but could no longer be found on the tree by July, neither in its previous position nor near the base of the tree.
This colony of Cinara piceae shared the rather small tree (about 4 metres high) with populations of Cinara piceicola and Cinara pruinosa . All three species were vigorously and effectively attended and defended by southern wood ants (Formica rufa). Carter & Maslen (1982) note that although the species is sometimes ant attended, this is not a necessary association as substantial colonies have often been found on young spruce within recently afforested wet grass moorland.
Binazzi & Scheurer (2009) also describe ant attendance for Cinara piceae as optional, whilst Völkl & Novak (1997) suggest that the intensity of ant attendance varies throughout the year. Working in Russia, Novgodorova (2005) found that Cinara piceae was tended by several Formica species but not by Lasius or Myrmica species. Gibb & Johansson (2010) investigated the factors affecting honeydew harvesting from Cinara piceae and Cinara piceicola by the red wood ant (Formica aquilonia) in managed boreal forests in Sweden. The rate of honeydew harvesting from recently clear-cut stands was similar to that in old stands but significantly faster than in middle aged stands. The high level of activity in clear cut stands was because of the abundance of spruce seedlings with high aphid loads, a feature we have also noted.
Damage and control
Carter & Maslen (1982) report that it is usually only a few trees that support extensive colonies. Where colonies have been feeding bark may show signs of cracking and bleeding and there may be needle desiccation. In heavy infestations the tree stem may become covered with sooty mould growing on the honeydew.
Kilpelainen (2003) worked with mixed populations of Cinara piceae and Cinara pruinosa attended by Formica ants. They found that wood ant-aphid mutualism was associated with a clear positive but non-significant height growth response in individual 5-year-old Norway spruce seedlings, but had a small significant negative effect on the stem growth of individual fast-growing 30-year-old Norway spruces. However, again only a small number of trees were infested. Delfino & Binazzi (2002) reported that infestations of Cinara piceae caused economic damage in Argentina.
On the benefit side, the aphid is welcomed by bee-keepers in Europe because it provides an important source of forage for bees and produces excellent honey.