Stem Defects in Sitka Spruce Induced by Sitka Spruce Weevil, Pissodes strobi (Peck.) : Insects Affecting Reforestation. Biology and Damage

1989

6 Abb., 7 Lit. Ang.

Unselbständiges Werk

9091

200069384

The effects of attack by the Sitka spruce weevil (=white pine weevil), Pissodes strobi (Peck.), on Sitka spruce trees, Picea sitchensis (Bong.) Carr. are described. The study was based on records of attack collected for 10 years (between 1959 and 1968), in a stand located near Nitinat Lake, British Columbia. The stands ws revisited in 1984 and tree quality was rated based on stem form. Also, the consequences of each attack in the period 1959-1968 for the quality of the stem in 1984 was determined. Twenty-six percent of the trees in this severely attacked area were rated as having good form; 51% had a medium form and 23% were so deformed that their conditin was rated as poor (no good for lumber). The trees sustained an average of 2.4 attacks per tree in the 1959-1968 period. These attacks resulted in an average 1.6 defects per tree. In 36% of the attacks studied the tree was able to develop one single stem and appeared normal, without external symptoms of attack. The remainder of the attacks developed into various defects as follows: scar 9%, minor crook 45%, major crook 7.3% and fork 2.7%. It was concluded that the Sitka spruce weevil caused a severe productivity depletion of the stand surveyed.