My work concentrates on feeding behavior of overwintering diapausing and post {--} diapausing bark beetles and developmental treshold. This is done either biochemically by measuring the enzymatic activity in the midgut and by assessing the feeding status from the size and consistence of the food bolus in the gut. Detailed knowledge of feeding behaviour and development treshold may help to predict the overwintering success of local populations with all the consequencies for spring dispersal and reproduction.

I used Moderate-Resolution Imaging Spectroradiometer (MODIS) imagery to answer two ecological questions. In the first project, I investigated the interactions between bark beetle-caused tree mortality and fire occurrence in western U.S. forests. I used remotely sensed fire data detected by MODIS satellite and bark beetle-caused tree mortality data. I tested the hypothesis that there is an increased probability of fire incidence in bark beetle-damaged forests compared to healthy forests using conditional probability modeling across the national forests of the western U.S. regardless of forest type. My results did not show a consistent pattern (increase or decrease of conditional probability of fire occurrence, &#;CP) across all lag time periods considered. However, when &#;CP is averaged across the 5-year study period (2001-2005) fire probability increased at 2-year (16%) and 3-year (9%) lags with 0, 1, 4, and 5-year lags showing no positive effect of bark beetle activity on fire probability. Further, when I analyzed fire-bark beetle-caused tree mortality separately for persistent fires (fires that lasted for at least two 8-day composite periods per season) and transient fires (fires that lasted for only one 8-day composite period per season), the &#;CP increased in all lag periods except the 5-year lag for persistent fires. In the second stage of this project, I used a non-parametric modeling approach to test how important bark beetle-caused tree mortality is in influencing fire occurrence relative to other climate and topography-derived variables in spruce-fir, Douglas-fir, lodgepole, and ponderosa pine forests. My results showed that climate and topography-derived predictors were consistently selected as important predictors of fire occurrence while bark beetle-caused tree mortality showing the least importance. In the second project, I predicted the invasive potential of a Puerto Rican frog species in Hawaii using the following MODIS products: land surface temperature; normalized difference vegetation index and enhanced vegetation index; and leaf area index/fraction of photosynthetically active radiation absorbed by plant canopies. My predicted maps showed that the invasive frog species in Hawaii is likely to expand its current habitat. My results also showed that MODIS-derived biophysical variables are able to characterize the suitable habitats of the invasive frog species.

Bark beetles regulate forest succession by removing weakened or stressed trees and exposing understory species to light from canopy gaps. Subterranean termites are predominate decomposers of coarse woody debris in southern pine forests; however, little is known about their role in forest health and succession. Both groups of insects rely heavily on fungal symbioses to fill their respective ecological niches in southern pine forests. During recent inspections of southern pine timber, we observed that trees in the early stages of bark beetle attack often had subterranean termites in blue-stained portions of the trunk. The frequency of subterranean termite presence in blue-stained areas of trees increased proportionally to the stage of bark beetle attack. However, practically no research has undertaken the challenge of describing how woody resources created by bark beetles are identified and utilized by subterranean termites before any signs of stress are visible. Therefore, this study examined possible facilitative interactions between subterranean termites, bark beetles and their blue-stain fungal associates, and other invertebrates, and investigated the effect of blue-stain fungi on surface properties of wood. Both native (Reticulitermes spp.) and Formosan subterranean termites exhibited a higher feeding preference for blue-stained sapwood than for unstained sapwood in laboratory assays. Native subterranean termites also consumed blue-stained sapwood at a higher rate than decayed wood. This study was the first to demonstrate that wood containing a non-decay fungus could elicit a feeding response from subterranean termites greater than that observed for decayed wood. Additionally, the surface properties of bark beetle-attacked southern pine were initially reduced by blue-stain fungal infection; however, the process of kiln-drying reversed this effect, resulting in a surface that was more conducive to wood product manufacturing.

This study examined the role of olfactory and visual cues in host finding of the pine bark beetles Hylastes ater and Hylurgus ligniperda and the burnt pine longhorn beetle Arhopalus ferus. The ultimate aim of this research was to provide new information on attractant and repellent (such as non-host leaf volatiles) stimuli to improve monitoring methods and reduce the attack by wood-boring and bark beetle species. A field trapping trial of visual and olfactory cues near Nelson caught 7842 H. ater, 274,594 H. ligniperda and 16,301 A. ferus adults. There were significant effects of both visual (colour and sihoutte) and olfactory (host and non-host volatiles) cues for all three species. The highest catches were in black (host mimicking), panel flight intercept traps baited with attractant (α-pinene and ethanol) and the lowest in clear or white (non-host mimicking) control traps. The repellent, green leaf volatiles (GLV) ((E)-2-hexen-1-ol & (Z)-3-hexen-1-ol) when present on traps with attractant reduced catches significantly but modestly in H. ater and H. ligniperda, but had no significant effect on A. ferus. A field trial near Christchurch found that GLV applied as a topical repellent halved the number of beetles attacking Pinus radiata logs. This reduction was significant in H. ligniperda, but not quite (P = 0.07) in H. ater. Placing logs among broadleaved plants (natural sources of non-host volatiles) significantly reduced attack of H. ligniperda by about 75% compared to logs in the open, but had no effect on H. ater. Attack by H. ater was found on 4% of 500 P. radiata seedlings in a field trial near Dunedin. Treatment of seedlings with GLV significantly affected the severity and proportion of seedlings attacked by H. ater, compared with insecticide-treated and control seedlings, but the treatment effect was apparently driven by an unexpected direct damaging effect of GLV on the health of seedlings. It is recommended that future research explores the use of non-host volatiles from natural sources that influence host finding in wood–boring and bark beetle species for the protection of plantation forests in New Zealand.

The phenology of the three exotic pine bark beetles present in South Africa was determined in the south-western Cape Province. Results from weekly trapping of adult beetles using trap-logs over a period of five years showed that the different species had activity peaks at different times of the year. Hylastes angustatus was the most consistent with 95% of the beetles captured in September and October. The Orthotomicus erosus activity peak was more variable but always occurred in the summer months (October to February) when 84% of the beetles were captured. Hylurgus ligniperda was the most variable, being found in every month of the year, although an autumn peak representing 37% of the beetles occurred in April/May. Activity peaks of each species coincided with distinct climatic conditions. Buried and partially-buried pine logs placed vertically in the soil to simulate roots and stems of seedlings were used to determine the colonisation sites of the three bark beetle species. Ninety-eight percent of O. erosus beetles were found in the protruding parts of the logs while 86% of H. ligniperda beetles were found mainly below soil level. H. angustatus were intermediate, entering the logs at or just below the soil interface but colonising mainly the buried parts in which 64% of the beetles were found. Both H. angustatus and H. ligniperda were able to detect and colonise logs buried horizontally at depths of 400mm, but O. erosus beetles were unable to do so. For adequate protection of seedlings from bark beetles, insecticide should be applied to both stems and roots. The phenology of the indigenous pine needle feeders Oosomus varius (Curculionidae) and Prasoidea sericea (Chrysomelidae) was determined by counting, at weekly intervals, the number of beetles present on 10 young pine trees. The O. varius activity peak occurred in August where 42% of all beetles were active, with 87% of the beetles present in July, August and September. P. sericea also had their activity peak in August when 60% of all beetles were active, but with August and September alone accounting for 87% of the beetles. The occurrence of the activity peaks was consistent each year over the five-year study period. This information facilitates the correct timing of prophylactic insecticide sprays.

Two study plots containing Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) newly infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) were established and photographed with large-scale (1:1000), colour infrared film on July 29. 1979 - approximately three months after possible insect attack. Ground checking confirmed attacked trees and also showed that at the time of photography all trees had visually green, healthy-appearing foliage. All trees, both attacked and non-attacked in each plot were matched to their photographic images, and visual photo interpretation for damage types and densitometric analysis of the original transparencies were done. For each tree-crown image included, the yellow, magenta and cyan dye layer density measurements were taken and these values plus three ratios derived from them were tested statistically using analysis of variance and stepwise discriminant analysis. Significant differences were found between the optical density values of the images of healthy and attacked trees. The ratio values had much smaller variances than did the individual dye layer densities and all three ratios showed significant differences between healthy and attacked trees. Stepwise discriminant analysis produced significant separation of damage classes. Two-thirds of the successfully attacked trees were correctly classified and were confirmed by a second ground check in January, 1980. It is concluded that successfully beetle-attacked trees have a unique spectral signature than can be detected on colour infrared air photos approximately three months after initial attack when the trees still support visually green, healthy-appearing foliage. / Forestry, Faculty of / Graduate

The diploma thesis deals with the issues of the spruce monocultures in the relation to the incidence of the bark beetle (Ips typographus) in the Šumava National park. The aim of the thesis is not only to unify and arrange the information, but also find out the level of knowledge about this topic among the pupils of the ninth grade of the basic school. The work also shows the level of knowledge of the pupils about the related problems and what are their opinions and suggested solutions. The thesis is divided into the theoretical and practical part. The theoretical part consists of eight chapters, that are devoted to the history of the Šumava forests, pine tree monocultures with the closer focus on the Norway spruce (Picea abies), the differences among the "natural" and "economical" forest and to the uniqueness of the Boubín primeval forest. In one of the chapters we get information about the huriccane Kyrill and its effects on the Šumava forests and followed by the information about the bark beetle calamities and about the bark beetle on its own. The last two chapters are devoted the solution of the current situation in the Šumava forests and their future perspectives. The practical part of the thesis contains mainly of the questionnaire survey proceeded among the pupils of the ninth grade of the...

Chez les scolytes (Curculionidae : Scolytinae) réalisant des pullulations éruptives, les processus conditionnant l’intensité et la durée des pullulations sont généralement mal connus. Nous avons étudié trois facteurs susceptibles de moduler les pullulations d’Ips sexdentatus (Börner) : la compétition intraspécifique, les ennemis naturels et la température. Les densités de colonisation et le seuil critique de densité d’attaques sur arbres ont été estimés lors d’une pullulation, et les effets de ces densités sur la productivité et la fitness des insectes ont été mesurés en laboratoire. L’entomofaune associée au scolyte a été étudiée dans des peuplements de pins présentant différents niveaux de dégâts de l’insecte. Les effets thermiques ont été estimés via des élevages à différentes températures. Les densités de colonisation sur arbres, ou celle correspondant à la valeur du seuil critique, ont fortement affecté la productivité et la fitness d’I. sexdentatus. L’entomofaune associée était peu sensible aux niveaux de population du scolyte, dont la productivité a cependant été réduite par la durée d’exposition aux ennemis naturels. L’estimation des besoins thermiques de l’espèce a permis de calculer qu’un réchauffement de 1°C augmenterait les effectifs et permettrait l’apparition d’une troisième génération annuelle, tout en réduisant la fitness des insectes. La compétition intraspécifique serait un facteur critique de régulation des pullulations d’I. sexdentatus alors que les ennemis naturels joueraient un rôle plus secondaire. Une élévation de température pourrait aggraver les pullulations mais aussi réduire la fitness des insectes et augmenter la compétition intraspécifique. / For eruptive bark beetles (Curculionidae: Scolytinae), the processes affecting the intensity and duration of outbreaks are generally poorly known. We have investigated three factors that may affect the population dynamics of Ips sexdentatus (Börner), namely the intraspecific competition, the natural enemies and the temperature. Colonization densities and the critical threshold of attack densities on trees have been estimated during an outbreak. How such densities affected the productivity and fitness of the beetles has been evaluated under laboratory conditions. The insect community associated with the bark beetle has been characterized in pine stands exhibiting different damage levels. To assess the thermal effects, the insects have been reared at different temperatures. Colonization densities on trees, or equivalent to the critical threshold of attacks, dramatically affected both the productivity and fitness of I. sexdentatus. The associated fauna was loosely related to the population levels of the bark beetle, although the duration of the exposure to the natural enemies affected its productivity. The assessment of thermal requirements allowed calculating that an average warming of 1°C during the activity period would increase the population levels and number of generations per year, but also decrease the beetles’ fitness. Intraspecific competition is probably a critical regulating factor for I. sexdentatus, while natural enemies would rather play a secondary role. A temperature increase could aggravate the outbreaks, but this could be counterbalanced by a fitness reduction and an increase of intraspecific competition.

Nos recherches abordent, par une approche multidisciplinaire, l’écologie spatiale et la dynamique d’invasion du ravageur de l’épicéa Ips typographus (Coleoptera :Scolytinae) en Belgique. Bien que cette espèce ne puisse pas être considérée au sens strict comme invasive en Belgique où elle est implantée depuis le milieu du 19ème siècle, de très vraisemblables introductions de souches exotiques en provenance de Russie et des Pays baltes, en font un modèle exceptionnel pour l’étude de ces processus.<p><p>Une analyse en milieu urbain, suivant des transects centre-périphérie, a d’une part suggéré l’introduction probable de ces souches exotiques et d’autre part permis d’étudier ce ravageur forestier dans un milieu qui lui est a priori défavorable. Il en résulte que, malgré un effet de la structure urbaine sur l’abondance du scolyte, sa présence a été observée partout, y compris dans les zones densément bâties du centre de Bruxelles. Cela suggère, en terme de dispersion, que cette espèce est capable d’atteindre des arbres isolés, et en terme d’infestation, que tout épicéa constitue un hôte potentiel tant en milieu forestier qu’en milieu ouvert ou urbain.<p><p>Une étape préliminaire dans l’estimation des risques liés aux invasions biologiques est d’effectuer une analyse de filière, afin d’analyser les différentes voies d’introduction et les risques liés aux pays d’origine des marchandises importées. Sur base de l’analyse de l’ensemble des sources de données statistiques disponibles, nous avons déterminé l’ampleur du commerce de grumes d’épicéa entre l’est de l’Europe et la Belgique, les modes de transport utilisés, les origines et destinations des grumes, ainsi que la variabilité de la localisation et du nombre des différents points d’entrée de ces marchandises sur le territoire belge d’une année à l’autre, depuis le début des importations en 1996. Notre analyse illustre les difficultés inhérentes à ce genre d’étude, particulièrement au niveau de la disponibilité des données à une échelle appropriée.<p> <p>Par une approche de modélisation, nous avons envisagé différents scénarios de dispersion de souches introduites d’Ips typographus afin d’estimer l’expansion de celles-ci en Belgique.<p>Notre modèle a permis de mettre en évidence l’importance de la bonne connaissance de certains paramètres biologiques caractétistiques de l’espèce étudiée (phénologie, capacité de dispersion, taux de croissance). Par ailleurs, les volumes d’importation et la localisation des points d’entrée des marchandises semblent jouer un rôle secondaire.<p><p>Enfin, nous avons utilisé des marqueurs génétiques afin d’essayer de prouver l’introduction de souches russes et baltes du scolyte de l’épicéa en Belgique. Des échantillons ont été collectés dans neuf pays européens ainsi que sur l’ensemble du territoire wallon. La structure génétique observée n’a pas permis de mettre en évidence une différenciation entre les populations de l’est et de l’ouest de l’Europe. La présence d’haplotypes communs à l’est et à l’ouest rejoint l’hypothèse d’une homogénéisation des populations en relation avec le large pouvoir de dispersion du typographe. Cependant, un grand nombre de mutations a été observé entre 2 haplotypes. Des introductions d’origines lointaines telles que la Sibérie ne sont donc pas improbables.<p><p>Les résultats détaillés de chacune de ces études sont développés dans les différents articles constituant cette thèse. La discussion générale met ceux-ci en relation et aborde les perspectives découlant de nos recherches. / Doctorat en sciences, Spécialisation géographie / info:eu-repo/semantics/nonPublished

7 Abstract The genus Geosmithia Pitt (Ascomycota: Hypocreales) belongs to fungi living in symbioses with bark beetles. Its original strategy is association with phloeophagous bark beetles (Coleoptera: Scolytinae). The Geosmithia shows strong affiliation to vector (bark beetles) worldwide and the spectrum of host plants is delimitated by niche of vector. The genus includes the specialists to family Pinaceae, but also the generalists with wide range of host plants mainly belonging to broad-leaved trees. G. morbida changed its ecology from saprotrophic to pathogenic way of life and causes decline of Junglans nigra in the USA. Characteristics which allow its pathogenesis are not known. Another derived strategy, which occurred at least twice independently, is association with the ambrosia beetles. The ambrosia beetles create galleries in xylem with low nutritive value, and thus they cultivate ambrosia fungus, on which they are entirely nutritively dependent. The ambrosia fungi share convergent phenotype which leads to large terminal conidia and to ability of yeast growth. This master thesis is focusing on study of the features, which are important for individual ecological groups: the specialists to family Pinaceae, the pathogene, the ambrosia fungi and the generalists. It is becoming apparent that the most...