© 1998 Heron Publishing—Victoria, Canada
Histological response of resistant and susceptible white spruce to simulated white pine weevil damage
Elizabeth S. Tomlin (1), Rene I. Alfaro (2), John H. Borden (1) and Fangliang He (2)
1. Centre for Pest Management, Department of Biological Sciences, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada / 2. Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, B.C. V8Z 1M5, Canada / Received February 24, 1997
Summary
The traumatic wound response of families of white spruce, Picea glauca (Moench) Voss, resistant or susceptible to the white pine weevil, Pissodes strobi (Peck), were compared after simulated weevil damage. Leaders from 331 trees were wounded just below the apical bud in the
spring, coinciding with the natural time of weevil oviposition. A portable 1-mm diameter drill was used to drill 24 holes
per leader. Leaders were removed in the fall and examined for evidence of traumatic resin canal formation. Drilled trees had
a traumatic wound response 8 times greater than that of undrilled trees; however, undrilled trees also formed some resin canals
in response to unknown causes. In the drilled trees, the traumatic wound response extended into the lower part of the leader,
where it could possibly affect older larvae. Trees from resistant families responded with greater intensity than trees from
susceptible families, by producing multiple rings of traumatic resin canals. Trees from resistant families also responded
more rapidly than trees from susceptible families based on number of cells to the first ring of traumatic resin canals. Trees
from some resistant families exhibited no traumatic resin canal formation, showing considerable within-family variation and
suggesting that other resistance mechanisms might be important. In the year after drilling, there was a reduction in tree
diameter growth and trees suffered a reduction in constitutive resin canals in the bark, which suggests some energetic cost
of traumatic resin production. There was no indication that the extent of constitutive defenses, as measured by density of
cortical resin canals before wounding, was related to the ability to produce traumatic resin canals. Screening trees based
on their capacity to produce traumatic resin canals may be useful in selecting genotypes resistant to white pine weevil.
Keywords:
host resistance, Picea glauca, Pissodes strobi, traumatic resin canals.
