Tortrix viridana

Tortrix viridana

The Green oak tortrix (Tortrix viridana Linnaeus, 1758) is a lepidopter belonging to the Tortricidae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Subkingdom Eumetazoa,
Superphylum Protostomia,
Phylum Arthropoda,
Subphylum Tracheata,
Superclass Hexapoda,
Class Insecta,
Subclass Pterygota,
Endopterygota cohort,
Superorder Oligoneoptera,
panorpoid section,
Order Lepidoptera,
Glossata suborder,
Infraorder Heteroneura,
Ditrysia division,
Superfamily Tortricoidea,
Family Tortricidae,
Genus Tortrix,
Species T. viridana.
The term is basionym:
– Phalaena viridana Linnaeus, 1758.
The terms are synonyms:
– Phalaena flavipes Geoffroy, 1785;
– Tortrix coeruleana Sorhagen, 1881;
– Tortrix flavana Zincken, 1821;
– Tortrix intermedia Dufrane, 1957;
– Tortrix pflegeriana Vlach, 1942;
– Tortrix suttneriana (Denis & Schiffermüller) 1775.

Geographic Distribution and Habitat –
The Tortrix viridana is a small nocturnal moth that lives and reproduces in deciduous forests in Europe, North Africa and Asia Minor. It is present in most of Europe with the exception of Croatia. Its range extends to Azerbaijan, Asia Minor and Iran.
In Italy it is also present on the Islands.
This moth flies throughout the summer, having the larval stage in mid-spring, feeding on the spring shoots of oaks and holm oaks, (Quercus), the caterpillars and the chrysalis are eaten by birds.
In areas where its population is very abundant, it can cause defoliation of oaks and holm oaks.
The main host plant is represented by various species of Quercus (oak), but it can also be found on species of Fagus (beech), Acer (maple), Populus (poplar), Salix (willow), Carpinus (hornbeam), Vaccinium and Urtica (nettle).
Older larvae can sometimes complete their development on Rubus idaeus (raspberry).

Morphology –
Tortrix viridana is a moth whose adults have a wingspan ranging from 17 to 24 mm; smaller specimens with a wingspan of just 13 mm are known, but such undersized specimens are rare.
The forewings are light green in color while the hindwings are dark with white fringes. Delicate streaks are also visible in the wings.
The costal margin is white tinged with yellow.
The head, fore body, as well as fore wings are green.
Sexual dimorphism is not evident. There are specimens in which the green color is replaced by dull yellow or primrose yellow; these cases apparently represent a recurring genetic form and are not due to abrasion or discoloration.
The larva reaches 15-18 mm in length of green-grey or light olive green colour, the head is black-brown tending to black; the prothoracic shield is greenish-brown or grayish, marked with blackish-brown, often edged anteriorly with white, and with a pale midline of black thoracic legs.
The pupa is 10-12 in length, with black-brown to black coloration.
The eggs are light yellow in color and then become orange-brown, lenticular in shape, delicately carved and generally laid in pairs.

Attitude and biological cycle –
The Tortrix viridana overwinters as an egg laid very early, at the beginning of summer, on some year old twigs; often the deposition takes place in the axil of the lateral twigs, in the leaf scars, etc.
The eggs are protected by secretions and scales produced by the adults.
In spring, at the vegetative restart, around March, small larvae originate from these eggs which carry out their trophic activity on the young vegetation. These larvae reach maturity around the month of May. The larvae build shelters, with silky threads, inside the leaves and shoots; the shelter consists of the leaf folded downwards, to form a case inside which the larvae shelter, coming out only with the head to systematically gnaw at the leaf page.
There are 5 larval stages.
The adults appear towards the end of May and lay the eggs which will be destined for the winter. In this way this moth completes only one generation per year.

Ecological Role –
Tortrix viridana is a defoliator moth whose larvae feed mainly on plants belonging to the genus Quercus.
An intense maggot infestation can defoliate an oak tree. The adult female lays eggs next to the leaf buds, which the larvae consume when they emerge. As the larvae grow, they eat larger leaves and then roll up into a full-sized leaf to pupate.
The damage caused is determined by the larvae that feed on the leaves and shoots.
The damage is therefore determined by defoliation, more or less intense depending on the attack, loss of the top and weakening of the affected plants.
Although it is primarily a forest pest, damage is also caused to trees in parks, gardens and nurseries.
The fight systems have so far been based on chemical fight according to the criteria of guided and integrated fight; it is carried out only in the nurseries and makes use of the monitoring of the populations, through traps with sexual pheromones.
The traps are installed within the first fortnight of May; monitoring is essential to establish the evolution of the phytophagous population which fluctuates over the years.
The products used are the normal larvicides.
However, biological-biotechnological control is recommended.
This intervention can be implemented using, against the small larvae, the Bacillus thuringiensis ssp. kurstaki, as a biological insecticide.
In addition, growth regulators can also be used.
Mass trapping methods are being tested in natural environments or in public parks, using trapping traps, placed on the edge of woods/parks, one every 100 metres.
It should also be remembered that the wasp Ichneumon Dirophanes invisor is a specialized parasitoid that attacks T. viridana.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Russo G., 1976. Agricultural entomology. Special Part. Liguori Publisher, Naples.
– Pollini A., 2002. Handbook of applied entomology. Edagricole, Bologna.
– Tremblay E., 1997. Applied entomology. Liguori Publisher, Naples.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/286055036/original.jpg
– https://inaturalist-open-data.s3.amazonaws.com/photos/242694376/original.jpeg