Author: (Zeller, 1840)
Spruce bark tortrix
Species Overview:
Adult: 13-14 mm wingspan; forewing relatively broad, grey-brown, distal area finely irrorate with yellow-ochreous; median and subbasal fasciae well developed, outer margin of the latter strongly produced; whitish area between the fasciae coarsely strigulated or marked with dark brown costally and dorsally. Hindwing dark fuscous; underside of hindwing of male with an elongate-ovate patch of whitish scales along inner margin from base to tornus.
Egg: lenticular, white, becoming reddish a few days after oviposition; deposited at night in batches of two or three in fissures in the bark, usually at the base of the whorls, on 5-10 year old trees [eggs Cydia pactolana ].
Larva: ca. 11 mm long; head light brown, region of stemmata and postero-lateral margin darker; prothoracic and anal plates light brown; abdomen white, pinacula inconspicuous. The newly hatched larva is pale pink [Cydia pactolana larva in cocoon ].
Pupa: 6 mm long; in the larval habitation, in a silken cocoon amongst the frass near the entrance.
Taxonomic Description:
Male:
Cydia pactolana adult 1
Cydia pactolana male
Cydia pactolana adult 2
External characters: 13-14 mm wingspan. Forewing ground colour white or cream-white, suffused and overlaid with grey-brown except interspaces between black-brown costal strigulae, some of the interspaces producing metallic violaceous plumbeous striae, and a narrow median area between the fasciae which is coarsely strigulated or marked with dark brown costally and dorsally; distal area finely irrorate (tips of scales) with yellow-ochreous; fasciate markings dark brown; basal fascia obsolete; sub-basal fascia well developed, its inner edge diffuse, the outer edge well defined and strongly produced medially, the projection usually angular and truncate and sometimes reaching median fascia; median fascia well developed, moderately broad, sometimes constricted medially, its edges indented and irregular, broadening dorsally and confluent with pre-tornal marking; ocellus moderately well defined, containing three or four black dashes often fractured and sometimes reduced to a series of dots, edged laterally with metallic violaceous plumbeous striae, the inner stria connecting with the postmedian stria from costa; a sprinkling of black scales in subapical area; cilia concolorous with wing basally, otherwise grey, with a black sub-basal line interrupted subapically by a cream-white dash and usually by a similar dash above tornus and sometimes by a smaller one at tornus. Hindwing dark fuscous; cilia greyish white, with a fuscous sub-basal line. Underside of hindwing of male with an elongate-ovate patch of whitish scales along inner margin from base to tornus (Bradley et al., 1979).
male gen. Cydia pactolana
Genitalia: Ventral margin of neck of valva without protuberance. Sacculus angulate. Aedeagus open in distal lower side, upper wall sclerotized and falcate, apex pointed. Cornuti more or less arranged in a row.
Female:
Cydia pactolana female
External characters: Similar to male.
female gen. Cydia pactolana
Genitalia: Anterior margin of lamella postvaginalis with median processes, lamella postvaginalis slightly elongated laterally, posterior margin concave. Posterior part of ductus bursae and posterior part of ductus seminalis sclerotized; ductus bursae broad medially, folded. Corpus bursae with two small signa.
Variation:
Minor variation occurs in the clarity of the forewing markings. The ground colour may be heavily overlaid with brown and the markings obscured, only the white costal interspaces remaining distinct; the black dashes in the ocellus are sometimes very weak (Bradley et al., 1979).
Biology:
excrements and pupal skin
Cydia pactolana is an univoltine species. The flight period of the adults extends from the end of May to the end of June, depending on the temperature conditions. Oviposition occurs on the bark of the stem near the branch whorls of young spruce trees. The females live about 16 days. Sporadic infestations of trees older than 10 years is of no economic importance.
The young larvae penetrate into the bark and bore long tunnels of up to 4 cm long with a diameter of about 2 mm, or they make mines of 1.8 x 1.2 cm. Infestations can usually be recognized in June by the small piles of excrements, which are at first fine-grained and light to reddish brown. The piles become larger in the course of the summer, with large, dark-brown faecal pellets mixed with resin. Resin exudes from the bore hole and often flows far down the stem. The feeding tunnels run in all directions between bark and wood and are often widened. At high densities these tunnels may lead to girdling of the thin stems. In Central Europe the larvae stop feeding around the middle of October, when the temperature falls. They do not resume feeding, even when they are again exposed to high temperatures for longer periods. Continuing high temperatures, however, cause them to develop immediately. Diapause in this species is thus facultative. The larvae spend their diapause in a short silken tunnel that is connected with piles of faecal pellets. Feeding is usually resumed in April and lasts 22-43 days. Cydia pactolana has five larval instars.
Pupation takes place in May or June underneath piles of faecal pellets in the opening of the bore hole. Before emergence the pupa moves out of the pile of excrements for about two-thirds of its length by rotating motions. Emergence of the adult males starts 2-3 days before that of the females. Swarming of the adults takes place in the evening hours and continues until darkness without any movement over large distances. Copulation also takes place in the evening. The first eggs are laid not earlier than 2 days after emergence (Bogenschütz, 1991; Postner, 1978).
Host plants:
Picea abies, Picea pungens and Picea sitchensis; Larix.
Damage:
piles of excrements
Cydia pactolana damage
The larva tunnels into the bark, gnawing the cambium and constructing a silk-lined gallery which may encircle the shoot, sometimes killing the twig, or goes up and down the trunk, causing slight resinous exudation, the resin forming white streaks. The feeding sites can be recognized by yellowish or brownish frass at the entrance to the tunnel, the interior of which is free of frass.
A high density of larvae on a whorl may partially or entirely block the sap-transporting tissues in young spruce trees. Parts of the crown or the entire tops may become dry. More than 30% of the trees of a plantation may die during an outbreak. Secondary pests like Magdalis violacea (Linnaeus) (Curculionidae), Pityogenes chalcographus (Linnaeus), Pityophthorus pityographus (Ratzeburg) (both Scolytidae), and the spruce bark cancer Nectria fuckeliana Booth cause additional death among the trees (Bogenschütz, 1991; Postner, 1978).
Outbreaks of Cydia pactolana often take place after dry years. Young stands are considered vulnerable, especially those that grow on shallow soils or in soils that tend to puddle. Such soils dry out very easily in dry periods and are impervious to water in wet years. Gradations are favoured in stands where frost damage is common in the spruce trees. In addition, damage caused by game, by hail and by cutting of brushwood and by dense populations of lachnid colonies on the stems may favour infestations (Bogenschütz, 1991).
Distribution:
Central, Northern and Eastern Europe; Siberia. In Japan, the subspecies Cydia pactolana yasudai Oku occurs, feeding on Abies sachalinensis.
Pheromone:
Pheromone unknown.
Attractantia:
E 8Z 10-12Ac : 1
E 8E 10-12Ac : 1
(Booij and Voerman, 1984a)
or
Z 8-12OH
(Witzgall et al., 1996b)
Parasitoids:
Among the parasitoids, Ascogaster quadridentata (Braconidae) is the best adapted to follow an outbreak of Cydia pactolana in Europe. Its importance diminishes during the retrogradation in favour of Glypta tenuitarsis Thomson (Ichneumonidae) and other less important species of parasitoids. Both species mentioned are phenologically well adapted to Cydia pactolana. They emerge at about the same time as the host. Ascogaster quadridentata stings the eggs that have been deposited in the bark, Glypta tenuitarsis probably the neonate larvae in the bore tunnel.
The main pupal parasitoid species is Pimpla turionellae (Ichneumonidae), followed by a not yet identified species of Phaeogeninae (Ichneumonidae) (Bogenschütz, 1991; Bogenschütz, 1975).
1. Cydia indivisa (Danilevsky)
Cydia indivisa adult
Cydia indivisa larvae can also be found mining in the bark of Picea and Larix, and can also be found on Pinus and Abies. Adults have olive-green to brown forewings with a conspicuous white media-dorsal spot. The species occurs from Western Europe to the southern part of Eastern Russia.
Genitalia:
male gen. Cydia indivisa ; female gen. Cydia indivisa
Males can be distinguished by the narrower and longer cucullus, the shallower notch in the ventral margin of the valva and the sacculus which is more rounded ventrally before neck of valva. The aedeagus is not pointed apically.
Females can be distinguished by the shape of the postvaginal plate and the ductus bursae.
2. Cydia coniferana (Saxesen)
Cydia coniferana adult 1
Cydia coniferana adult 2
Another species of Cydia that can be found feeding in the bark of Picea is Cydia coniferana (Saxesen); it occurs from Europe to Eastern Russia and Mongolia, and its main host is Pinus sylvestris.
In both Cydia pactolana and Cydia coniferana the median fascia and basal patch are edged with a band of the whitish ground colour, but the bands are set much further apart dorsally in Cydia pactolana.
Genitalia:
male genitalia C. coniferana ; female genitalia C. coniferana
Males can be distinguished by the shape of the valva and cucullus (notice the pointed projection on the ventral margin of the valva in Cydia coniferana) and the shape of the aedeagus; females by the shape of the postvaginal plate and the width and sclerotization of the ductus bursae.