Adelges piceae (Adelgidae)

the balsam woolly adelgid

Adults:

Wingless, globoid form. Mouthparts composed of long threads called stylets, origin mid-ventrally: body covered with cottony tuft of wax strands.

Nymphs:

Small, flattened oval shape, was fringed.

Damage:

Damage to branches: Feeds on stem, branches and twigs. During feeding it injects a salivary substance into the tree which causes gall-like formations on the twigs and branches (gouting). Feeding activity on the bole of the tree causes dense wood formation similar to compression wood - such infestations, easily recognized by white "wool" covering the bole, usually kills the tree in a few years. "Gouting" may progressively weaken a tree over a long period of time.

Damage to bark and wood: Balsam woolly adelgid feeding on the bark stimulates an increased production of highly lignified xylem in the neighbourhood of feeding. The wood is dark, resinous, hard and brittle. See thumbnail below for the comparison of normal vs. reaction wood formation. Such reaction wood is known as rotholtz.

Principal Hosts:

True firs of the genus Abies. Kills and severely damages Pacific silver fir, A. amabilis, subalpine fir, A. lasiocarpa, and grand fir, A. grandis. No primary host is involved.

Economic Importance:

The damage symptoms listed above render the wood brittle and with excessive resin content. This lowers its value as a lumber and pulping species. Mortality of stands causes early harvesting which disrupts planned harvesting schedules.

References and Links:

FC: 107.

See HForest, Diseases and Insects in British Columbia Forest Seedling Nurseries, or JP17.

Additional Images: