Eastern spruce gall adelgid

Eastern spruce gall adelgid - Cross-section of young galls showing the interior cells and contents
  • Latin name: Adelges abietis (Linnaeus)
  • French name: Puceron à galle conique de l'épinette
  • Order: Homoptera
  • Family: Adelgidae
Description

Distribution

Canada

Micro-habitat(s)

Needle, Annual shoot

Damage, symptoms and biology

The damage caused by this insect consists of gall formation on annual shoots. In spring, the older nymphs, which have overwintered, are transformed into wingless adults and deposit their eggs near the buds. As a result of the stings from young, freshly hatched nymphs, the new needles become enlarged and form a pineapple-shaped gall. The gall is initially light green in colour with red spots, and turns brown and dries out at the end of the summer.

The presence of galls causes distortions of the twigs and the crown ultimately becomes misshapen. In some cases, the tree may die after a few years.

The adelgid produces two broods per year and all individuals are females. Over the summer and until fall, the cells in the gall open up and the nymphs emerge and change into winged adults. The latter deposit their eggs, which are coated with a mass of stringy wax, near the next season's buds. The nymphs that hatch from these eggs overwinter at the base of needles and buds.

Life cycle (East of the Rockies)

Life cycle (East of the Rockies)
Stage/Month J F M A M J J A S O N D
Egg
 
 
Nymph
 
 
Adult
 
 

Other information

An introduced species from Europe, the eastern spruce gall adelgid has been recognized as a pest of ornamental spruce since the 16th century in Europe. It was introduced from Europe prior to the 20th century and has since spread across the northeastern United States and southern Canada, to North Carolina. The adelgid is not common in the Maritimes or Newfoundland, whereas in Quebec and Ontario, it has wreaked considerable damage, particularly in 1941, in the southern part of both provinces.

A silvicultural method of control consists in cutting infested twigs and galls in mid-summer and destroying them (preferably through incineration) before the nymphs emerge in August.

Canadian Forest Service Publications

Eastern spruce gall adelgid

Diet and feeding behaviour

  • Sap-feeding : Feeds on plant sap.
    • Piercing-sucking: Has specialized mouthparts for sucking the fluids from plants, thereby causing deformities or killing the affected plant sections.
    : Feeds on plant sap.
    • Gall-forming: Induces the formation of galls and feeds on their tissues.
Information on host(s)

Main host(s)

Black spruce, Norway spruce, white spruce

Photos
  • Eastern spruce gall adelgid Cross-section of young galls showing the interior cells and contents
  • Eastern spruce gall adelgid Close-up of A. abietis adults, wings folded
  • Eastern spruce gall adelgid Gall on the new shoot
  • Eastern spruce gall adelgid Cells of galls which have opened naturally to release adults, still near the gall
  • Eastern spruce gall adelgid New spruce shoots bearing galls
  • Eastern spruce gall adelgid White spruce branch bearing several old galls
  • Eastern spruce gall adelgid Old gall in its natural state
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