LEVELS OF SITKA SPRUCE WEEVIL, PISSODES STROBI (PECK), DAMAGE AMONG SITKA SPRUCE PROVENANCES AND FAMILIES NEAR SAYWARD, BRITISH COLUMBIA

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Abstract
Variation in tree height, number of attacks by the Sitka spruce weevil (= white pine weevil) (Pissodes strobi [Peck]), tree form, and stem defect were studied in a 15-year-old Sitka spruce (Picea sitchensis [Bong.] Carr.) provenance test near Sayward, on Vancouver Island, B.C. An aggregated spatial distribution of the attacks was found in the plantation. Average number of attacks, tree form, and total tree height varied significantly among provenances and among families within provenances in both light and severe infestation patches. The number of unattacked trees varied by provenance from 5 to 51%, but in patches of severe infestation it varied from 0 to 64%. The number of attacks per tree had a significant negative effect on tree height. However, at the same level of attack, some provenances grew significantly taller than others. Thirty, 19, and 51% of all trees were classified as having a good, medium, or poor form, respectively. Among provenances located in severe infestation patches, the percentages of trees having good form varied from 4 to 64%. The type of defect that formed after an attack (minor crook, major crook, or fork) varied by provenance. Aggregated weevil attack and genetic differences among provenances may have accounted for this variation.