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endemic populations with pheromone traps to detect incipient outbreaks. Canadian-Entomologist
117(7): 839-848.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: The numbers of adults of Orgyia pseudotsugata caught in sticky delta-shaped
pheromone traps baited with different concentrations of synthetic lures were compared with eggmass
densities and subsequent tree defoliation throughout a population cycle in British Columbia.
A lure containing 0.01% pheromone by weight in the form of a 3 x 5-mm poly(vinyl chloride) rod
provided more consistent catches than pheromone concentrations of 0.0001, 0.001, 0.1 or 1.0%.
Trap saturation occurred when over 40 moths per trap were caught. To achieve a standard error of
30%, 6 traps were required at each site. There was a poor correlation between numbers of moths
caught and egg-mass density or defoliation estimates in the following generation, but a threshold
density was found that provides a warning of an incipient outbreak. Ground surveys for eggmasses
are recommended to confirm suspected infestations after continuous increases in moth
catches for 2-3 years or if an average of 25 moths or more per trap has been caught.
551. Shepherd, R.F., I.S. Otvos and R.J. Chorney. 1984a. Pest management of Douglas-fir tussock
moth (Lepidoptera: Lymantriidae): a sequential sampling method to determine egg mass density.
Canadian-Entomologist 116(7): 1041-1049.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: A sequential egg-mass sample system for Orgyia pseudotsugata (McDunn.) was
designed, based on visual scanning of the lower branches of Douglas firs (Pseudotsuga menziesii)
in British Columbia. A branch was removed from each quadrant from the upper, middle and
lower crown level, and from the lowest whorl of a total of 59 non-defoliated trees in 10 areas. No
consistent trend in egg-mass density per branch could be found between crown levels, so the
lower whorl of branches was selected for survey purposes. Sample stop lines were determined
from egg-mass density and variability data collected on 55 sites, and subsequent defoliation
estimates were related to these densities. The system is designed as an early detection tool to be
used only in non-defoliated stands at the incipient stage of an impending outbreak.
552. Shepherd, R.F., I.S. Otvos, R.J. Chorney and J.C. Cunningham. 1984b. Pest management of
Douglas-fir tussock moth (Lepidoptera: Lymantriidae): prevention of an outbreak through early
treatment with a nuclear polyhedrosis virus by ground and aerial applications. Canadian-
Entomologist 116(11): 1533-1542.
Keywords: tree/stand protection
tree/stand health
stand conditions
Abstract: Two application methods were tested using a nuclear polyhedrosis virus as a
biological control agent at an early stage in an outbreak of Orgyia pseudotsugata on Douglas fir
[Pseudotsuga menziesii] in British Columbia in 1981. The virus, which often leads to the
development of an epizootic late in the outbreak cycle, was propagated in O. leucostigma. Four
plots were treated from a helicopter at a dosage of 2.2 x 1011 polyhedral inclusion bodies (PIB)