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539. Schowalter, T.D., M.I. Haverty and T.W. Koerber. 1985. Cone and seed insects in Douglas-fir,
Pseudotsuga menziesii (Mirb.) Franco, seed orchards in the western United States: distribution
and relative impact. Canadian-Entomologist 117(10): 1223-1230.
Keywords: seed orchard management
tree/stand protection
tree/stand health
Abstract: Cones of Douglas fir (Pseudotsuga menziesii) were collected from 17 seed
orchards in California, Oregon and Washington in the autumn of 1983; they were dissected, and
seed losses were ascribed to Contarinia oregonensis, Megastigmus spermotrophus, Barbara
colfaxiana and Dioryctria abietivorella. There appeared to be great differences between orchards,
but overall C. oregonensis and M. spermotrophus collectively destroyed about 70% of the filled
seed. Physiographic province significantly explained variation in damage by all insect species
between orchards. In general, damage by all species increased from northern provinces to
southern mountainous provinces. Damage by C. oregonensis and B. colfaxiana appeared to be
related to land use management factors also.
540. Schowalter, T.D. and J.D. Stein. 1987. Influence of Douglas-fir seedling provenance and
proximity to insect population sources on susceptibility to Lygus hesperus (Heteroptera: Miridae)
in a forest nursery in western Oregon. Environmental-Entomology 16(4): 984-986.
Keywords: nursery operations
tree/stand protection
tree/stand health
Abstract: The effect of Lygus hesperus feeding on seedlings of Douglas fir (Pseudotsuga
menziesii) was measured in seedlings representing 2 elevation zones, for each of 2 seed zones,
and each of 2 seedling age classes in a forest nursery in Oregon during 1984. Damage frequency
and height reduction both indicated significant effects of seed source. Examination of seedling
distance from the nursery's west boundary with a lucerne field (a major source of L. hesperus in
the nursery) indicated a significant effect of proximity to alternative hosts. These results suggest
that seedling susceptibility to damage by L. hesperus is a function of seedling condition and
location within the vegetation matrix.
541. Schuch, U.K., M.L. Duryea and L.H. Fuchigami. 1989. Dehardening and budburst of Douglas-fir
seedlings raised in three Pacific Northwest nurseries. Canadian-Journal-of-Forest-Research 19(2):
198-203.
Keywords: nursery operations
tree phenology
tree physiology
Abstract: Two-yr-old Douglas fir (Pseudotsuga menziesii) seedlings from 2 seed sources
raised in 3 nurseries in Oregon and Washington were tested to see how nursery location affected
dehardening (the seasonal transition from a frost-resistant to a frost-susceptible condition) and
budburst between Jan. and Mar. 1986. The seedlings were measured with a whole-plant freezing
test. In general, seedlings raised at the nursery at the highest alt., and in a few cases trees from the
most northerly nursery, were more frost resistant than trees from a coastal nursery. From Jan. to
Mar., seedlings from the highest (975 m) seed source had less hardy stem tissue than seedlings