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Western spruce budworm : behavior and monitoring with sex-pheromone traps Sweeney, Jonathan David


The main objectives of this thesis were to: determine the roles of the minor components, 89/11 (E/Z⁰) 1 1-tetradecenyl acetate (AC) and 85/15 (E/Z) 11-tetradecenol (OH), of the sex pheromone of the western spruce budworm, Choristoneura occidentalis Freeman, in the orientation and pre-copulatory behaviors of the male moth; and, to evaluate various combinations of pheromone concentration, trap design, and maintenance regime for monitoring the budworm. The behavior of the male moths was observed, in a wind tunnel and in the field, in response to virgin females and to synthetic sex pheromone components, alone and in blends. The pheromones were incorporated into polyvinyl chloride rods at concentrations from 0.00005-0.5% (w:w) and release rates were estimated by gas-liquid chromatography of volatiles captured on Porapak-Q. OH contamination in lures of the major component, 92/8 (E/Z)-11-tetradecenal (ALD), and the AC, made it impossible to determine precisely the effects of either AC, ALD, or ALD+AC on the behavior of the male moth, but still allowed the testing of blends of ALD+AC+OH which resembled those released by virgin females. The moths were from three sources: a long-established non-diapausing laboratory colony; wild budworms collected near Ashcroft, B.C.; and crosses between laboratory males and wild females (lab-wild). The threshold concentration of ALD necessary to stimulate upwind flight was between 0.0005 and 0.005%; response peaked at 0.05% and dropped off above this concentration. The net upwind ground speed of flight decreased significantly at higher concentrations of ALD in the laboratory moths, and as the moths approached the lure with all three populations. In most experiments, the virgin female stimulated a greater percentage of males to contact the lure, and a faster upwind net ground speed of flight, than did ALD at about the same release rate. AC and OH stimulated response on an electroantennogram, but by themselves were not attractive to males in the wind tunnel. The addition of OH to 0.05% ALD significantly decreased the percentages of males locking-on (0.5% OH) and flying upwind (0.005% OH) in wild and lab-wild moths respectively, and significantly increased the percentage copulatory attempts of lab-wild males (0.005% OH). In the lab-wild males, a blend of ALD+AC+OH approximating that from a virgin female significantly increased the percentages of upwind flights, lure contacts, and copulatory attempts over those to ALD alone. The total blend, and not just the major component, affected long range behavior of the male moth. The laboratory males appeared less sensitive to the addition of minor components to 0.05% ALD than did the wild or lab-wild males. The mean total season's catch/plot in five non-maintained Uni-traps, baited with 0.05% ALD, was significantly correlated with the number of larvae/m² foliage in the same generation (r = 0.97), but only when a lower valley plot with very low larval density was excluded (plot 12). Correlations were significant (P ≤ 0.10) between larval density/plot in 1985 and the total moth catch/plot (n = 1 trap/plot) in 1984 in sticky traps (r = 0.45) and Uni-traps (r = 0.44) baited with 0.05% ALD and maintained. The latter correlation was significantly improved (r = 0.67; ≤ 0.05) when plot 12 was excluded. The addition of plot basal area/ha or foliage biomass/ha as independent variables significantly improved the coefficient of determination for the regression of larval density/plot in 1985 vs total seasons catch/plot in 1984, but again only when plot 12 was excluded. Of the trap systems evaluated, the Uni-trap, baited with 0.05% ALD, showed the most promise for monitoring the western spruce budworm, but permanent sample plots will have to be established and followed for several years to determine whether the system can be operational.

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