Cooley spruce gall

From an email by Jocie to the Botany Group on January 30.

Fanciful-looking Cooley spruce galls add a splash of colour to these grey, dreary days. Many have funky shades of purple, red and yellow. They vary depending on what stage they are at— older galls are dull brown.

I’ve been noticing just how abundant these galls are on the branch tips of local Sitka spruce wherever I go. I’ve also seen plenty up the mountain on the Engelmann spruce that’s been planted along the Jutland ski trail. See some photos below (click a photo to enlarge it).

The galls are caused by a tiny aphid, Adelgid cooleyi, with a complex life history (6 generations! – see the diagram below). Interestingly, the aphid requires more than one conifer species to complete its life cycle. For this species, the alternative host is usually Douglas fir (it’s called the Douglas-fir adelgid on iNaturalist). The adults look like tiny dots of white wool (see the reference below for photos). I haven’t seen these on Douglas fir needles before but it’s something to look out for!

I confess that I know nothing about spruce galls, but they are interesting to look at on a dull winter day! To learn everything you might ever want to know about them, you can download this document from the Forest Genetics Council of B.C. It’s worth looking at just to see all the great photos of different stages.

If any of you are spruce gall experts, or have anything to add to this discussion let me know.

  1. Cooley’s spruce gall on Sitka spruce: Little River Nature Park (1).
  1. Cooley’s spruce gall on Sitka spruce: Little River Nature Park (2).
  1. Cooley’s spruce gall on a snowy Sitka spruce (Union Bay).
  1. Cooley’s spruce gall on Engelmann spruce (Jutland ski trail, Mt Washington).
  1. Cooley spruce gall life cycle.
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