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The objectives of this presentation are to (i) review measures taken by various agencies in British Columbia to
elucidate the interrelationship between the weevil and its host, (ii) discuss studies in progress to take advantage of the genetic
resistance of the host and (iii) present an overview of attempts to control one of the more destructive forest pests. The
presentation will also review future plans.
Prince George Progeny Trials
WEEVIL RESEARCH
Field Studies
Due to the importance of interior spruce in British Columbia, a decision was made to embark on the genetic improvement
of the species complex in the early 1960's. The senior author was hired to carry out this project in 1967.
The basic approach to improving interior spruce was to designate geographically distinct areas (selection units or
SU's) and select trees based on size and form in each selection unit (Kiss and Yeh 1988, Kiss and Yanchuk 1991). The first
of these selection units was in the Prince George area. A total of 180 parent trees were selected. Cones and scions were
collected from most selected parents. Scions were used to establish clone banks, and seeds were used to establish genetic
tests.
As part of the improvement program, genetic tests were established using open-pollinated progenies of individual
parents selected in various selection units. The first set of these tests, representing the Prince George SU, was established in
1972 and 1973 (Kiss and Yeh 1988, Kiss and Yanchuk 1991) using the open-pollinated progenies of 173 parent trees.
The initial objective of the genetic tests was to identify well-performing families based on the growth performance of
their progenies. This information aided in the construction of rogued first generation seed orchards and helped to identify
candidates for advanced generation breeding. To this end, periodic height measurements were carried out and at age 15
diameter measurements were also made.
Following the 15-year height and diameter assessments, heavy infestation of white pine weevil was observed at some
test sites. Cursory observation appeared to suggest a pattern to the infestation. Further studies confirmed this pattern and
revealed the possibility of genetically controlled resistance mechanism(s) in a number of families. Results of this study are
reported by Kiss and Yanchuk (1991).
In summary, the results showed that:
1. While there were different intensities of attack at the three individual test sites in the Prince George SU tests
(i.e., 9% at Quesnel, 37% at Red Rock, and 63% at Aleza Lake), there were significant correlations between
families attacked across sites (Figs. 1 and 2).
2. The estimate of family-mean heritability for weevil resistance across sites was high (h2f=0.77 + 0.11).
3. Families exhibiting greater vigor at any age were generally more resistant. Correlation between 6-year family
height and incidence of weevil attack was negative and significant (Fig. 3, r=-0.42), as well as 15-year height
and incidence of weevil attack (Fig. 4, r=-0.68). In fact, when families were ranked based on height growth at
different ages, and average attack was calculated for the top and bottom 25% of families, the top families
always had significantly lower attacks than those of the bottom families (Table 1).
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