Spruce seed moth (Cydia strobilella)

(Written by Dr. Herb Cerezke)

Last Review/Updated: January 6, 2003

Larvae of the spruce seed moth (Cydia strobilella (L.)) feed within the cones of spruces, sometimes causing serious losses of the seed crop.

Primary Hosts and Distribution

  • White spruce (Picea glauca (Moench) Voss)
  • Engelmann spruce (P. engelmannii Parry)
  • Black spruce (P. mariana (Mill.) B.S.P.)

The spruce seed moth occurs throughout Alberta, attacking cones in wild stands and in established seed orchards.

Life Cycle

The spruce seed moth has a one-year life cycle, but a variable portion of the larval population can undergo extended diapause for up to three years.

Larvae

Larvae are creamy white with a brown head capsule and measure about 10 mm long when mature. Larvae first appear in female conelets shortly after pollination, develop through four instars during the summer, and mature in late summer when they excavate a tunnel in the central cone axis to overwinter.

Pupae

This stage develops in the central cone axis in spring and is light to dark brown in color and about 5 mm long.

Adult Moths

Moths are a smoky brown color with silvery crossbands on the forewings and a wingspan of 8 - 11 mm. They appear in May about the time of pollination.

Eggs

Eggs are pale to dark orange, spherical, about 0.5 mm in diameter, and are deposited between cone scales during or shortly after cone pollination.

Detection and Damage


  • Male moths can be captured in sticky pheromone-baited traps in May;
  • Infested cones have no external signs or symptoms of larvae being present;
  • Cones bissected lengthwise in late summer show larvae in tunnels within the central cone axis;
  • In infested cones, seeds may be partially or completely consumed and fused to the scale and with silken tunnels between seed pairs

Percentage of cones infested in a cone crop is variable from year to year and in different locations, but can be as high as 70% of cones. Each larva destroys about 30% of the filled seeds per cone.

Management

  • Presence of moth populations can be monitored with pheromone-baited sticky traps. Numbers of male moths caught may indicate the relative abundance of this insect in seed orchards.
  • Sampling of young conelets after pollination can serve to detect the presence of eggs and young larvae and form the basis for predicting infestation levels later in the season.
  • Dissection of cones can be undertaken to monitor for larvae, pupae, and for estimation of percentage seed loss.
  • Because larvae overwinter within cones, the removal of mature cones from the seed orchard in the fall also removes the resident population.
  • Application of systemic insecticides to foliage, soil, as stem injections and as stem implants are effective for reducing populations in seed orchards.