Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 214-221).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 175-182.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 203-236).

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Gnathotrichus retusus is primarily univoltine with a minor fraction of the population taking more than one year to complete the life cycle. From the spring to the summer, the development of brood from egg to adult took about 40 days or more in Douglas-fir logs. Brood production was significantly related to the gallery length. Boring activities were not consistently related with temperature, shifting from shallow sapwood to deep sapwood over time. Fungal staining was usually limited to the wood near the gallery entrance, and became darker in colour over time beginning in June. Abandonment of some galleries mainly occurred in June and July by females, and was probably induced by high temperatures. G. retusus preferred Douglas-fir stumps to western hemlock stumps, but both host tree species were equally suitable for G. retusus brood development. Significant differences were found among individual Douglas-fir and western hemlock stumps in attack density and brood production. Within a stump, attack density and brood production for Douglas-fir, and attack density for western hemlock increased from the stump top to the bottom. G. retusus emergence from Douglas-fir and western hemlock stumps and G. retusus and G. sulcat us flights began in late April when the daily maximum temperature reached 13.5°C, and peaked in late May. Brood emergence of G. retusus ceased, with rare exception, in late June. G. retusus had only one big peak flight while G. sulcatus had a small second peak flight in late July. Seasonal flights ceased in October when weekly mean maximum temperatures dropped below 15°C. Brood emergence, seasonal flights, and the sex ratios of brood ready to emerge and captured flying beetles were positively correlated with maximum temperature. G. retusus had a bimodal diurnal flight rhythm: a very small morning flight and a much larger dusk flight. Light intensity seemed to be a major stimulus in initiating the flight. However, diurnal flight might also be influenced by both temperature and relative humidity. Both G. retusus and G. sulcatus of both sexes responded significantly to ethanol or their own aggregation pheromones, (+)-sulcatol and (±)-sulcatol respectively, and ethanol was a synergist of (+)-sulcatol for G. retusus of both sexes. Alpha-pinene was neither a primary host attractant nor a synergist of aggregation pheromones. The sex ratios (female/male) of both species increased significantly from less than one for host chemicals alone to above one for treatments including aggregation pheromones. The sex ratio of G. sulcatus increased with increases in release rates of (±)-sulcatol. / Forestry, Faculty of / Graduate

A commercial sawmill in British Columbia, Canada, was surveyed in 1979 for the presence of the ambrosia beetles Trypodendron lineatum (Olivier) and Gnathotrichus retusus (LeConte) using pheromone-baited traps. The temporal and spatial distribution and relative abundance of these species were determined. This information was used during 1980 and 1981 to develop a mass-trapping program for these species while maintaining the integrity of an existing trapping program for a third ambrosia beetle species, G. sulcatus (LeConte). A fourth ambrosia beetle species, Platypus wilsoni (Swaine) responded in significantly larger numbers to traps baited with the pheromone sulcatol plus ethanol and α-pinene than to those baited with the pheromone lineatin or unbaited. Several experiments were conducted in order to improve or assess the trapping system. It was found that both G. retusus and T. lineatum response to their respective pheromones was increased by the inclusion of ethanol and α-pinene on the traps. T. lineatum response to lineatin was significantly reduced when sulcatol was included in the bait. An experiment conducted to determine optimum trap height showed that largest numbers of T. lineatum were caught on the lowest traps that cleared surrounding understory vegetation. A mark-recapture technique was tested as a potential means of assessing trapping efficiency. Recommendations were made that could result in this technique becoming a useful means of optimizing and evaluating ambrosia beetle mass-trapping programs. This concurrent mass-trapping program for three species of ambrosia beetles demonstrated that large numbers of beetles can be captured using pheromone-baited traps. The relatively low cost of this pest management tactic compared with the high values at risk has already resulted in much of the technology developed in this thesis being incorporated in ambrosia beetle management programs by forest industries in British Columbia. / Forestry, Faculty of / Graduate

Les insectes coléoptères Scolytinae, ou scolytes, sont des agents biotiques majeurs de perturbation des écosystèmes forestiers à travers le monde. Ils peuvent être avoir des impacts écologiques et économiques sévères en milieu naturel et dans les plantations forestières. La dynamique et l’écologie des scolytes des forêts tempérées, boréales et méditerranéennes ont été abondamment documentées, définissant un cadre conceptuel approprié pour l’étude de ces insectes dans d’autres écosystèmes forestiers où les connaissances restent parcellaires. C’est le cas des forêts néo-tropicales équatoriales, au sein desquelles les communautés de scolytes restent à ce jour relativement méconnues, malgré leur implication croissante dans les dégâts et mortalités observés dans le cadre du changement global et du remplacement des forêts naturelles en plantations forestières. Dans cette thèse, je me suis intéressée aux facteurs climatiques et écologiques qui régissent la diversité et l’impact des scolytes dans des forêts naturelles et dans des plantations de balsa (Ochroma pyramidale) en Equateur, ainsi qu’aux associations scolytes-champignons mises en place chez certaines espèces dans ce milieu. Ce travail a permis d’enrichir les connaissances actuelles que les connaissances actuelles sur la diversité des scolytes en Equateur. J’ai pu montrer notamment que les différents types d’habitats forestiers (forêts naturelles et plantations de balsa) influencent davantage la composition en espèces que la richesse spécifique cumulée. Il existe par ailleurs des espèces indicatrices de ces habitats, dont l’une d’entre elles est un ravageur majeur du balsa dans les plantations (Coptoborus ochromactonus), et trois autres sont des espèces exotiques. L’étude spécifique de la biologie et de la dynamique des populations de C. ochromactonus dans les plantations de balsa a montré que des facteurs climatiques et d’âge des arbres influencent significativement les dégâts occasionnés par ce scolyte. Enfin, j’ai pu mettre en évidence l’association des champignons ambrosia Raffaelea sp. nr. arxii et Fusarium ambrosium avec des scolytes Xyleborus, l’un des genres les plus diversifiés et abondants en forêt naturelle et en plantation de balsa. Ma thèse de nouvelles perspectives en termes de biodiversité et de gestion des risques sanitaires liés aux scolytes dans les écosystèmes forestiers d’Equateur.Mots-clés: scolytes, richesse, abondance, composition des espèces, forêt primaire, balsa, dégâts, phénologie, interaction plante-insecte, champignon ambrosia, Xyleborus / Scolytinae insects, or bark beetles, are major biotic agents of forest ecosystem disturbance throughout the world. They can have severe ecological and economic impacts in both natural forests and commercial plantations. The dynamics and ecology of bark beetles in temperate, boreal and Mediterranean forests have been extensively documented, defining an appropriate conceptual framework for the study of these insects in other forest ecosystems where knowledge remains fragmented. This is the case of the equatorial neo-tropical forests, in which bark beetle communities remain to date relatively unknown, despite their increasing involvement in the damage and mortality observed in the context of global change and the replacement of natural forests by plantations. In this thesis, I focused on the climatic and the ecological factors driving the diversity and impact of bark beetles in natural forests and in balsa (Ochroma pyramidale) plantations in Ecuador, as well as in scolytines-fungi associations that can take place in a number of scolytine species. This work has enriched current knowledge on the diversity of bark beetles in Ecuador. In particular, I have shown that different types of forest habitats (natural forests and balsa plantations) have a greater influence on species composition than on cumulative species richness. I also identified indicator species of these habitats, one of which is a major pest of balsa in plantations (Coptoborus ochromactonus), and three others are exotic species. The specific study of the biology and population dynamics of C. ochromactonus in balsa plantations has shown that climatic and tree age factors significantly influence the damages caused by this bark beetle. Finally, I was able to highlight the association of ambrosia fungi Raffaelea sp. nr. arxii and Fusarium ambrosium with Xyleborus bark beetles, one of the most diverse and abundant genera in natural forest and balsa plantation. My thesis provides stimulating new perspectives in terms of biodiversity and management of health risks related to bark beetles in forest ecosystems of Ecuador.Key words: scolytine, richness, abundance, species composition, primary forest, damage, phenology, insect-plant interaction, ambrosia fungi, Xyleborus