Lachnus roboris
Lachnus roboris
The black aphid of the chestnut or variegated aphid of the oak (Lachnus roboris L.) is a homopterous Rincote belonging to the Aphididae family.
Systematic –
From a systematic point of view it belongs to the Eukaryota Domain, Kingdom Animalia, Eumetazoa Suborfer, Superphylum Protostomia, Phylum Arthropoda, Subphylum Hexapoda, Insecta Class, Pterygota Subclass, Exopterygota Cohort, Subcoorte Neoptera, Paraneoptera Superorder, Rhynchotoidea Section, Rhynchota Order, Suborder Homoptera, Section Sternorrhyncha, Superfamily Aphidoidea, Family Aphididae, Subfamily Lachninae and therefore to the Genus Lachnus and to the Specie L. roboris.
Geographic Distribution and Habitat –
The black aphid of the chestnut is a species of aphids, which feed on species of the genus Quercus or Castanea, present in Europe, in the Mediterranean region and some in the Middle East.
Morphology –
The Lachnus roboris is an aphid whose winged adults measure up to 6 mm in length and the spotted forms reach 4 mm in length. The insect is characterized by having the body of blackish color, slender and with long legs; the wings are transparent with black speckles.
The taxonomy of the Lachnus roboris is however somewhat uncertain and Blackman & Eastop (1994) suggest that it is a complex of species with different karyotypes on host plants. In this case the species present on Castanea could be a different species. However, Dixon & Thieme (2007) finds the Lachnus roboris that feeds on both Quercus and Castanea.
Attitude and biological cycle –
The Lachnus roboris infests both oak and chestnut trees, especially the younger lignified branches and the suckers, in a period that goes from the beginning of the spring vegetative revival up to the autumn.
The sessupare and then the anfigonic forms occur in September-October and produce the durable brown-blackish-glossy eggs on the branches; the eggs are laid, close to each other, in large numbers so as to cover the bark.
The black aphid of the chestnut tree carries out a mono-helix with the appearance in spring of the attending foundresses; from these, for parthenogenesis, the founded fondatrigenias originate a series of spring-summer generations. In these generations appear winged virginogenies that spread the species on other plants thanks to the ability to fly on the various plants.
Ecological role –
Infestations of Lachnus roboris cause damage that consists of general decay. In the event of heavy infestations, in addition to general vegetative decay, there is a lower quality production.
Moreover the Lachnus roboris is almost always frequented by ants, usually by wood ants; these consume large quantities of honeydew produced by this species and in return (at least in the case of wood ants) actively defend the aphids against predators (symbiotic action).
As for the containment of this aphid, it is not normally implemented. In the case of heavy infestations, especially on young plants or in nurseries, it is possible to intervene with winter treatments on durable eggs. The products to be used are the white oils possibly activated, for winter treatments; or, in the spring-summer period, on plants infested with mobile forms and always in the nursery, you can intervene with specific aphids or phosphorganics. The eventual use of these active ingredients must however be commensurate with the presence and the biological cycle of useful insects and its possible antagonists in order not to benefit the Lachnus roboris.
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.