Identification and Control Methods of the Spruce Cone Moth

Spruce cone moth [Cydiastrobilella (Linnaeus)], also known as the spruce cone leaf roller, belongs to the order Lepidoptera, family Tortricidae. In China it is distributed in Heilongjiang, Inner Mongolia, Shaanxi, Gansu, Ningxia, Qinghai, ** and other places, mainly damaging spruce and larch.

Damage characteristics: the larvae damage cones and seeds; infested cones become curved and exude resin, and after falling the cone scales often do not open.

Morphological characteristics

The adult is about 6mm long, with a wingspan of 10-13mm. Head, thorax and abdomen are grayish black. The labial palps project forward and curve slightly upward, with sparse long scale hairs. The brownish black forewings are narrow and long; the light black basal patch protrudes forward at its middle; the median transverse band is brownish black, extending from the middle of the costal margin to near the anal angle of the hind margin, with its middle slightly arched and protruding; from the middle of the costal margin to the apex there are 3-4 groups of grayish white, glossy hook-shaped markings, which extend downward into 4 silvery gray oblique patches with metallic luster reaching the hind margin, anal angle and outer margin. The hindwings are pale brownish black, lighter at the base, with yellowish white fringe hairs.

Eggs are round or slightly flattened, yellow.

The larva is 10-11mm long, slightly flattened, yellow-white to yellow. The head is brown, and the postoccipital area is rather shiny. The spiracles are very small and brown. On the last body segment, the spiracles are located on both sides of the midline.

The pupa is 4-5mm long, brown. The frons is protruding; the projections on the penultimate segment bear spines, and there are 4 hook-shaped anal spines.

Occurrence pattern: 1-2 years per generation, overwintering as mature larvae. In early April the overwintering larvae begin activity; from early May to mid-June they pupate, with the peak in mid-May; from early May to mid-June they emerge and lay eggs, with the peak in mid- and late June; from early June to early July they hatch, with the peak in mid- and late June; from late July to late August the mature larvae enter the cone axis to overwinter.

Adult emergence is mostly concentrated from 9:00 to 15:00, and they are active in flight from 8:00 to 16:00; after emergence the pupal shell is slightly exposed beyond the scales. After 1-2 days the adults mate and lay eggs, with a female-to-male ratio of about 2.36:1, and a lifespan of about 5 days. Eggs are laid singly on the inner side of the cone scales of young cones, above the seed wing; one cone has 1-6 eggs, with a maximum of 29 eggs; each female lays 34-105 eggs, averaging 53, and more eggs are deposited on the sunny side of the crown than on the shady side. After hatching, the larvae bore into the scales and tunnel toward the young seeds, feeding on the immature endosperm, then move into adjacent seeds to continue damaging them; each damaged seed has 2 holes, and the larvae can move back and forth among the seeds they feed on; after the larvae mature, they bore into the cone axis and overwinter in an oblong chamber, with a few overwintering in the scales and damaged seeds. Infested cones become curved and exude resin, and after falling the cone scales often do not open. This insect is more abundant on sunny slopes and on the sunny side and upper part of the crown; its density is greater in young stands, open forests and pure forests than in middle-aged and old forests, dense forests and mixed forests.

Natural enemies include 2 species of parasitic wasps and 1 species of parasitic fungus; about 65% of overwintering larvae are often pecked and eaten by birds.

Control methods

(1) Agricultural control.

Create mixed forests, strengthen tending, improve tree vigor, and prevent damage; in conjunction with seed collection, remove infested cones and dispose of them centrally.

(2) Protect and utilize natural enemies.

(3) Chemical control.

At the peak of larval hatching, spray omethoate 500-fold solution, which gives good control results.

Commonly used agent: omethoate.