I doubt root aphids are the only small white bug you can find in the roots.
That+myc?
I'm confident in the diagnosis. Check this picture, identical to what I'm seeing.
The most likely suspects seem to Pachypappa tremulae or Prociphilus xyloster.
Some copied info here:
The coniferous root aphid, Pachypappa tremulae, previously called Rhizomaria piceae, has been a pest at several British Columbia nurseries, particularly near Prince George. Infestations (
Figure 90) are most common on container seedlings. Bareroot stock is rarely affected. This aphid's major hosts are container-grown spruce, potted spruce grafting stock, and sometimes pine, larch, and Douglas-fir. To date, infestations on otherwise healthy seedlings have caused no damage; this may not be true for stressed seedlings. Little is known about this aphid's life history, damage, or distribution. The aphids, which are usually most abundant on the exterior roots in the upper portion of the container cavity may go unnoticed until the seedlings are lifted. They secrete white waxy strands that might be mistaken for mycorrhizae. Part of the aphid's life cycle occurs on trembling aspen Populus tremuloides leaves, which may explain the predominance of infestations at nurseries in the north central Interior.
