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Cooley Spruce Gall Adelgid

Characteristics:

  • Eggs: Females reproduce without mating. They lay their eggs near needle buds in the spring and hatch 2 weeks later.
  • Larvae: Once hatched, adelgids suck sap from the base of new needles.
  • Nymphs and adults: Both nymphs and adults are 1 millimetre long and can be light to dark brown in colour. Nymphs mature in July or August and can over winter on spruce as nymphs. Adults wrap themselves in a white, waxy wool and look like white cottony specks on the underside of needles.

Identifying infestations:

  • Needle deformation or ‘galls’ at the tip of branches Each year, the first generation of adelgids will develop a gall (thicken branch tip) at the base of new needles on evergreen trees. The gall is 2.5 to 5 centimetres in length and are first light green in colour, then turn to a dark purple. Once the galls have ‘opened’, they will harden and turn brown as it dries out. Old galls can remain on a tree for 2 to 3 years.
  • White, cottony specks on the underside of needles Adult adelgids cling to the underside of needles and look like tiny white cotton specks.

IPM Toolkit:

  • Preventive tools:
    • Keep your tree healthy as heavy infestations can indicate environmental stress.
  • Physical tools:
    • Remove galls in June before they open to reduce adelgid populations and improve the appearance of trees.
  • Biological tools: Not applicable
  • Least toxic chemical tools: Not applicable