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stand conditions
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Abstract: Following aerial application of a nuclear polyhedrosis virus of Orgyia
pseudotsugata against this lymantriid on Douglas fir (Pseudotsuga menziesii) in British Columbia
in 1982, the impact of treatment was studied in 1983 and 1984. The virus appeared to have spread
from treated plots to adjoining areas in 1982, effectively reducing lymantriid populations. This
observation suggests the spraying of alternate swaths to reduce the amount of microbial pesticide
used. A naturally occurring viral epizootic reduced lymantriid populations in 2 of 3 check plots in
1983, but severe tree mortality occurred in 2 of these plots, with 60 and 62% of sample trees dead
in 1984. The corresponding tree mortality in 2 of 4 treated plots was 4 and 7%.
450. Otvos, I.S. and R.F. Shepherd. 1991. Integration of early virus treatment with a pheromone
detection system to control Douglas-fir tussock moth, Orgyia pseudotsugata (Lepidoptera:
Lymantriidae), populations at pre-outbreak levels. Forest-Ecology-and-Management 39(1-4):
143-151.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: The development and integration of a pheromone monitoring system with a
nuclear polyhedrosis virus treatment is described. Stands of Douglas fir (Pseudotsuga menziesii)
in British Columbia susceptible to tussock-moth outbreaks are defined by overlying maps of past
outbreaks, forest and habitat types, and climatic zones. Pheromone-baited traps are placed and
monitored annually at permanent locations in susceptible areas. Measuring annual trends of moth
density indicates time and location of the next outbreak. Trap-catch data provide an early warning
of impending outbreaks, confirmed by ground reconnaissance. Insect density and defoliation are
predicted from egg-mass and larval sampling. The virus can then be applied from the air or from
the ground into threatened stands to initiate an epizootic to prevent development of an outbreak
and to minimize tree damage. The virus appears to spread, and field tests with reduced dosages
indicate that the small amount of virus applied can still greatly reduce larval populations and
prevent tree mortality, at considerably reduced cost.
451. Overhulser, D.L., J.D. Walstad and R.P. Bowers. 1980. Twig weevil damage to Douglas-fir
seedlings and a field test of Dursban for control. Tree-Planters' Notes 31(2): 17-20.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: Damage categories are described for young platations in Oregon mostly 2+1
seedlings, planted in 1975-76 and surveyed in 1977 after attack by Cylindrocopturus furnissi in
1976. A test using Dursban 4E (chlorpyrifos) spray at 0-4% a.i., applied in July 1977, showed
n.s.d. in % damaged trees between treated and control areas after 4 months, but this may have
been due to a natural decline in weevil numbers. Spraying with 2% a.i. Dursban in Aug. 1977
significantly reduced the numbers of weevils present.
452. Owens, J.N. 1987. Development of Douglas-fir apices under natural and cone-inducing
conditions. Forest-Ecology-and-Management 19(1-4): 85-97.
Keywords: seed orchard management