Powderworm on Texada Island

On December 7th, 1999 I visited the northern end of Texada Island with Jan-Evert Hermans to track down some current powderworm infestations in western red cedar. At Raven Bay we inspected second growth western red cedar (photo 1) that had been felled for three weeks. Top ends of logs were searched for frass-filled galleries in the heartwood. Only two logs in the whole setting showed any symptoms. Short sections of one the infested log were sawn and split at the heartwood/sapwood interface (photo 2) to reveal any gallery patterns inside the log. The relatively few galleries seen in cross-sections actually proved to be a symptom of a massive gallery formation inside the log.(photo 3)

Further splitting of a log showed a larval "tail" (=abdomen) hanging out of a gallery (photo 4). Careful splitting of the log freed the larva completely (photo 5). The larva had the characteristic dorso-ventrally flattened and laterally expanded thorax (photo 6). The larva was estimated to be nearly mature-probably Trachykele blondeli.

The major symptom that log buyers look for in a log they suspect may have powderworm is the larval galleries on trimmed branch ends (photo 7) . The trees on Texada Island had been felled for only three weeks. The mature larva indicated that the infestation occurred as long as two years ago so clearly living trees can have active infestations. You may have noted that there were no galleries in the sapwood of the split log. Larvae gain entry to the heartwood of the log by boring down through the branch pith and follow the dead wood through the "knot" and finally bore out of the branch stub where it originates in the heartwood.

At this time there is no known treatment for the powderworm. It has been reported from low altitudes (<300m) coastal forests in White Rock, Point Grey, the Sunshine Coast, the Gulf Islands and other coastal locations north to Campbell River.

Photographs by Jan-Evert Hermans of Swevik Enterprises Ltd.