Author: (Hübner, 1799)
European fir budworm
Species Overview:
Adult: 17-24 mm wingspan; forewings brownish grey with darker indistinct markings and dark transverse wavy lines; hindwings grey.
Egg: green, elliptical, about 1.5 x 1.2 mm; 10-30 eggs deposited in two rows.
Larva: approximately 22 mm long; head black, abdomen green with darker line dorsally and black pinacula; prothoracic shield divided, brown-black; anal shield brownish-yellow.
Pupa: 8-14 mm long, dark brown; cremaster with eight hooked setae.
Taxonomic Description:
Male:
Choristoneura murinana male 1
Choristoneura murinana male 2
External characters: Head, thorax and abdomen brown-grey. Forewing with a very narrow costal fold reaching to middle of costa. Ground colour brownish grey, weakly shining, with dark transverse wavy lines. Basal field, median fascia and subcostal blotch darker; markings indistinct. Cilia yellowish brown at base, with dark line, whitish terminally. Hindwing grey; cilia whitish with brown line (Kennel, 1908-1921).
male genitalia C. murinana
apex of sacculus C. murinana
apex aedeagus C. murinana
8th sternite in Choristoneura spp.
Genitalia: Tegumen narrowed posteriorly as viewed antero-dorsally; median length as long as width at base; lateral side nearly straight or slightly convex as viewed antero-dorsally. Uncus narrow, gently curved; widest part of subapical area 1.5- to 2.0-fold basal width; ventral area of apical third with fine and short unbranched setae. Socius well developed, almost as long as uncus, curved ventro-anteriorly; anterior margin distinctly emarginate at midlength; dorsal area of distal half with dense, long and upcurved setae. Gnathos smooth, C-shaped in lateral view; straight length from base to apex shorter than that of socius. Transtilla bulbous medially and microscopically spiculate. Aedeagus gently curved, moderately sclerotized; left side of distal half sharply narrowed ventro-apically; opposite side slightly narrower than width at midlength; apical margins oblique, thickened and well sclerotized; dorsal apical angle with dorsally or dorso-anteriorly directed conical spine; aedeagal surface with numerous fairly coarse spicules; cornuti lanceolate. Valva subtriangular, as long as basal width. Sacculus smooth, ventral margin gently sinuate with short setae; dorsal margin sharply raised into sharp ridge; distal end expanded mesoposteriorly forming subquadrate plate as viewed ventrally.
8th sternite with long median process (Dang, 1992).
Female:
Choristoneura murinana female 1
Choristoneura murinana female 2
External characters: As in male; without costal fold.
female gen. C. murinana
Genitalia: Caudal margin of lamella postvaginalis with small incision medially.
Antrum delicately sclerotized; ductus bursae long, shorter than in Choristoneura diversana.
Biology:
Choristoneura murinana is a univoltine species. The main flight period is from the end of June until the end of July. Females prefer to lay their eggs on the upper side of needles in the tops of full-grown trees. Egg masses are usually deposited in two rows and consist in general of 10-30 eggs. Larvae hatch after approximately 2 weeks and disperse by lively crawling, but they may also be transported by the wind. Larvae usually hibernate in the crown of the trees, where they spin themselves in protecting webs in sheltered places, e.g. bark crevices. They moult there about 5 days after hatching and enter diapause. The larvae leave the hibernacula between late April and mid May of the following year, depending on the ambient temperature. In this time the larval population is largely redistributed within and between the trees due to passive dispersal caused by the wind. The larvae attach a web between two neighboring buds or between a bud and a needle, from where they penetrate into the already open buds and start to feed. The larvae spin needles together to form a tunnel during the stretching of the shoot. Second to fourth instar larvae chew holes in the growing needles. The tunnels are left when the larvae have reached the fourth larval instar. The larvae then move towards the tops of the trees, where they continue to feed on young needles. They spin new webs that are only left after disturbance. From the fifth instar onwards, larvae bite through needles at about the middle of their length. The tops of the needles are fixed to the tunnels with webbing threads. Needle stumps and tops are chewed to small remnants. These remnants discolour and give the fir crown a reddish appearance. Choristoneura murinana has a total of six larval instars. The feeding period following hibernation lasts 6-8 weeks. Each larva consumes about 120 needles.
Pupation takes place inside the webs at the last feeding place. The adults emerge after approximately 14 days and live maximally 3 weeks (Bogenschütz, 1991).
Host plants:
Choristoneura murinana feeds virtually only on silver fir, Abies alba. Other hosts (Picea, Larix, Pinus, Juniperus, Fagus) may sometimes be attacked as a result of mass outbreaks, but are normally of no importance to the fir budworm.
Damage:
This species is considered to be the main needle destroyer of Abies alba. The losses in growth are economically of less importance than the weakening of the trees, which may lead to considerable secondary attacks by pest species and pathogens and eventually may cause death of the trees. The gradual thinning out of the woods soon lead to degradation of the soil due to an increase in the ground water table, and to overgrowth by grasses and, for example, by Rubus idaeus Linnaeus and Sambucus racemosa Linnaeus. Rejuvenation is thus seriously hampered. Young plants may also be directly affected by feeding of the larvae falling of the trees (Bogenschütz, 1991).
Distribution:
Northern and Central Europe; Caucasus, Eastern Russia.
Pheromone:
Z 9-12Ac : 0.5 *
E 9-12Ac : 0.02
11-12Ac : 0.05 *
Z 11-14Ac : 0.02 *
12Ac : 0.03 (Priesner et al., 1988)
Components marked with * are involved in attraction.
Parasitoids:
Of egg:
Trichogramma minutum (Riley) (Trichogrammatidae)
Of larva:
Blondelia nigripes (Fallén) (Tachinidae)
Pseudoperichaeta nigrolineata (Walker) (Tachinidae)
Pseudoperichaeta palesoidea (Robineau-Desvoidy) (Tachinidae)
Apanteles murinanae Capek and Zwölfer (Braconidae)
Ephialtes calobata (Gravenhorst) (Ichneumonidae)
Ephialtes terebrans (Ratzeburg) (Ichneumonidae)
Cephaloglypta murinanae (Franz) (Ichneumonidae)
Ephialtes inquisitor (Scopoli) (Ichneumonidae)
Of pupa:
Apechthis quadridentata (Thomson) (Ichneumonidae)
Apechthis rufata (Gmelin) (Ichneumonidae)
Itoplectis maculator (Fabricius) (Ichneumonidae)
Itoplectis alternans (Gravenhorst) (Ichneumonidae)
Pimpla turionellae (Linnaeus) (Ichneumonidae)
Pimpla instigator (Fabricius) (Ichneumonidae)
Phaeogenes maculicornis (Stephens) (Ichneumonidae)
Monodontomerus aereus Walker (Chalcididae)
Patocka, 1960, provides a full list of parasitoids recorded from this species.