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. / Forestry, Faculty of / Graduate

Thesis (M.A.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xi, 80 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 72-77).

No description available.

Tree-ring chronologies from ten mixed conifer stands in the Colorado Front Ranges and New Mexico Sangre de Cristo Mountains were used to reconstruct timing, duration, and radial growth impacts of past outbreaks of western spruce budworm, Choristoneura occidentalis Freeman. Graphical and statistical comparisons of tree-ring chronologies from host and non-host tree species, in conjunction with Forest Service records of outbreaks during the twentieth century, revealed that outbreaks were identifiable only in the host chronologies as sharply reduced growth periods. These comparisons also showed that host and non-host tree-ring chronologies were generally similar between outbreaks and that both were responding in a similar manner to climatic variation. A study of defoliation and insect population data that was available for the New Mexico stands demonstrated that host radial growth from 1978 to 1983 was highly correlated with budworm activity. The non-host chronologies from each stand were used to correct the host chronologies for climatic and other non-budworm environmental variations by a differencing procedure. The corrected chronologies were then used to estimate the dates and radial growth effects of past budworm outbreaks. Tree-ring characteristics of twentieth century documented outbreaks were used as criteria for inferring the occurrence of outbreaks in previous centuries. At least nine periods of increased budworm activity were identified in the region from 1700 to 1983. The mean duration of reduced growth periods caused by known and inferred budworm outbreaks was 12.6 years, and the mean interval between initial years of successive outbreaks was 34.9 years. The mean maximum radial growth loss was 50 percent of expected growth, and the mean periodic growth loss was 21.6 percent. There was an unusually long period of reduced budworm activity in the first few decades of the twentieth century, and since that time outbreaks have been markedly more synchronous between stands. Increased synchroneity of outbreaks in the latter half of the twentieth century suggests that areal extent of outbreaks has increased. This phenomenon may be due to changes in the age structure and species composition of forests following harvesting and fire suppression in the late nineteenth and early twentieth centuries.

Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographies. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 126-143). Also available on the World Wide Web.

The western spruce budworm, Choristoneura occidentalis Freeman (Lepidoptera: Tortricidae), is a serious defoliator of conifers in the western U.S. and western Canada. In 1985 epidemic levels of the budworm caused average tree defoliation in west-central Idaho to increase to 83%, up substantially from the 35% average tree defoliation of 1984. Associated with this increase in defoliation was a change in the relative stand defolation ranking between the two years. found to damage all types and In 1985 the budworm was developmental stages of reproductive structures of Douglas- fir, including: seedcone buds, pollen-cones buds, maturing cones, and seeds. Differential selection of feeding sites was observed, with a significantly higher proportion of larvae found in seedcone buds than in pollen-cone buds. Shortly after larval emergence, 25% of the total number of seed-cones buds were infested. A subsample of 171 branch tips indicated that only 9% of pollen-cones, while less than 2% of the vegetative buds contained larvae. A total of 640 cones from 21 trees were examined. Of these cones, 76% were infested with larvae, however not all of the seeds were destroyed. The average percent of destroyed seeds per tree was found to be exponentially related to the average current defoliation of the tree.

Thesis (M.S.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 35-41). Also available on the World Wide Web.

I assessed the relationship between natural disturbances and climate in Douglas-fir forests in western North America. I quantified synchrony within disturbance types, explored the potential for synergism between disturbance types, and analyzed changes in disturbance dynamics that have occurred following Euro-American settlement of western North America. I used new and previously published dendrochronological reconstructions of disturbance histories and climatic variability to explore these complex interactions at multiple spatial scales over the last three centuries. I used dendroentomological methods to reconstruct western spruce budworm outbreaks at thirteen sites along a transect running from central Oregon to western Montana. These forests experienced repeated, often decadal-length western spruce budworm outbreaks over the last three centuries. I compared my records with previously published outbreak reconstructions and found widespread synchrony of outbreaks at stand-level, regional, and sub-continental scales. At ten of my sites, I also reconstructed or obtained previously published reconstructions of fire dates. I compared these disturbance histories with dendroclimatological drought records to quantify the influence of moisture availability on disturbances. I found that fires were more likely to occur during drought years, while western spruce budworm outbreaks were most likely to begin near the end of droughts. After approximately 1890, fires were largely absent from these sites and western spruce budworm outbreaks became longer-lasting, more frequent, and more synchronous, likely due to land-use induced changes in the structure and composition of forests. My results show no discernible impact of defoliation events on subsequent fire risk. Any effect from the addition of fine and coarse fuels during defoliation events was too small to detect given the overriding influence of climatic variability. If there is any relationship between the two disturbances, it is a subtle synergistic relationship wherein each disturbance type dampens the severity but does not alter the probability of occurrence of the other disturbance type over long time scales. This dissertation includes unpublished co-authored material. / 10000-01-01

Future climate changes will alter disturbance regimes worldwide with important implications for many ecological and social systems. In west central British Columbia, Canada, fire and insect disturbances have shaped the historic character of Douglas-fir (Pseudotsuga menziesii var. glauca Beissn. Franco) dominated forests. However, since AD 1900 fire suppression and other forest management practices have led to denser forests and conifer encroachment into grasslands. Considering climate changes in interior British Columbia are expected to result in warmer and drier conditions, understanding the influence of climate on forest disturbances is crucial for land managers tasked with both mitigating the effects of disturbance and promoting resilience in forest ecosystems. This research focused on developing multi-century, annually-resolved records of fire and western spruce budworm outbreaks to evaluate: the historic climate conditions related to these disturbances; the influence of grassland proximity on disturbance-climate relationships; and, whether western spruce budworm outbreaks were related to fire activity. At the landscape scale, a detailed study in the Churn Creek Protected Area revealed spatially variable stand structure and fire-climate relationships at a low elevation forest-grassland ecotone over the interval AD 1600 to 1900. This finding suggests the site was characterized by fires of mixed-severity dominated by frequent, low-severity, fires related to positive antecedent moisture conditions punctuated by widespread fires of moderate to high severity related to intervals of persistent drought. At the regional scale, the influence of interannual climate variability and large-scale patterns of climate variability (e.g. El Nino Southern Oscillation) was evaluated using new and existing records of fire history and multiple climate pattern reconstructions. Regional fire activity was shown to be significantly related to interannual climate variability, and no consistent patterns between regional fire years and the individual phases or phase combinations of large-scale patterns of climate variability were detected. The findings suggest that the spatial expression of large-scale climate patterns translates into weak and undetectable terrestrial effects related to fire activity in this region. The influence of grassland proximity on disturbance history was investigated using site-level and regional tree-ring reconstructions of western spruce budworm outbreaks and fire activity based on four sites adjacent to grasslands and four sites not adjacent to grasslands between AD 1600 and 1900 (fire) and AD 1600 and 2009 (western spruce budworm). Fires affecting grassland proximal sites were more frequent than fires occurring in forests not adjacent to grasslands, and the character of western spruce budworm outbreaks was generally consistent among all sites. Fire activity was related to both warm, dry and cool, wet conditions in the fire year and/or year(s) preceding the fire depending on proximity to grasslands, suggesting climate conditions associated with both fine fuel growth and drying are key determinants for fire activity. The initiation of western spruce budworm outbreaks was significantly related to drought and this relationship was enhanced at sites adjacent to grasslands. At the site-level and regional scale, no consistent association was found between the initiation of western spruce budworm outbreaks and fire years indicating the historic interaction between these disturbances is weak or non-existent. / Graduate