Graduation date: 1971

An analysis was made of the distribution of and interactions between three major species of insects in cones of Douglas fir. This was based on over 3,500 cones from 93 trees in 1961 and 4,000 cones from 97 trees in 1962. High variation in damage was found among trees for each of the three insect species studied (Contarinia oregonensis Foote, Megastigmus spermotrophus Wachtl., and Dioryctria abietella D.&S.) In C. oregonensis this variation was significantly related to the height of the trees and dates when cones became pendent. The percentage of filled seeds and average cone size of the trees were important in M. spermotrophus. The average cone size of the trees and duration of vegetative bud flushing were significantly associated with D. abietella. The within tree-variation of damage by C. oregonensis was highly significant and consistant from tree to tree and year to year. Damage increased significantly from the bottom to the top of live crown. Suggestions are made to help increase the seed yield by chemical control of insects by selection of uninfested or slightly infested trees by sequential sampling, and by selection of cone and seed insect resistant trees for seed orchards. Although no tree was wholly resistant to all three insects the best, with only 4.8 per cent of its seeds damaged, was so much better than average that it may be of considerable economic importance. The great range in apparent resistance of trees to attack by cone and seed insects should be recognized in further studies and attempts be made to determine biologically sound reasons for the observed differences. / Forestry, Faculty of / Graduate

The paper describes a Douglas-fir classification for the interior of British Columbia which was developed for the purpose of identifying trees susceptible to the attacks of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopk. The significance of the depredations of the beetle to the objectives of sustained-yield forestry is discussed and the need for control and continuous protection stressed. A method of direct control of bark beetles is exemplified and receives criticism for its laborious-ness, high cost, and temporary protection. It is noted that foresters and entomologists are increasingly cognizant that forest management should strive for insect control through the development and maintenance of forest conditions unfavourable to insects. These conditions become manifest in vigorous forests which possess an inherent resistance to insect attack. By harvesting on a selective and critical basis the forest may be made relatively resistant and insects can be controlled by indirect means. Detailed reference is made to a system of indirect control developed for ponderosa pine forests against the attacks of the western pine beetle, Dendroctonus brevicomis Lec. The theory, development, and application of the system is considered and later referred to in the light of the results of the present study. The possibility of developing similar systems for other insects and hosts is demonstrated from the literature. Similarly, the ability of other workers, to classify Douglas fir into vigour and age groups is shown. In view of the apparent feasibility of judging the susceptibility of classes of Douglas fir to attack by beetles an attempt was made to develop a classification which might have value in this regard. A classification was developed and tabulated from data collected at Westwold, B. C. in the interior Dry Belt at an elevation of 3,000 feet. The method is described in detail and the limits of the four vigour classes and of the four age groups are statistically justified. The classification was tested for its accuracy in judging actual and relative age and vigour at Westwold and also at Lumby in the interior Wet Belt. The results of the tests are tabulated and the reason for the high degree of accuracy in judging actual vigour in terms of diametral growth attributed to the measurements of phloem streaks. Infested trees were objectively classified on an area of eight square miles at Westwold to determine which classes of vigour and age were susceptible to attack. The results reveal that the older, slower growing trees are most susceptible. Specifically, trees of over 150 years of age with a ten-year diametral growth of less than 11 millimetres are most likely to be infested. The type of host selection made by the Douglas-fir beetle is compared to a combined thinning from below and a selection cutting of the older age classes. It is suggested that, in forests subjected to endemic populations of beetles, trees of classes 2D, 3C, 3D, 4C, and 4D be harvested to increase the vigour and resistance of the residual stand and to implement indirect control. / Forestry, Faculty of / Graduate

Fusarium spp. are among the most important pathogens of Douglas-fir (Pseudotsuga menziesii) seedlings in bareroot nurseries. Currently the most effective disease control method is soil fumigation with methyl bromide. As methyl bromide is phased out, however, other disease management strategies may become more important. We explored two alternative approaches to management of Fusarium diseases in Douglas-fir seedlings. The first approach was to transfer certain components of conifer forest soil, where Fusarium usually does not occur, to nursery soil, where Fusarium is often abundant. Specifically, we tested two hypotheses: (1) conifer forest soil contains a greater proportion of bacteria antagonistic in vitro to Fusarium than does nursery soil, and (2) pine needles, humic acid, ectomycorrhizal fungi, or bacteria obtained from forest soil will protect Douglas-fir seedlings against disease caused by soilborne Fusarium spp. if added to nursery soil. We did not find conclusive evidence to support either hypothesis. The second approach was to investigate the potential for biological control of seedborne Fusarium. Previous workers have shown, and we have confirmed in our studies, that Fusarium present on a small percentage of Douglas-fir seeds before cold stratification may spread during stratification; we recovered Fusarium from nearly all stratified seeds, representing three seedlots, plated on three culture media. When these seeds were planted in pasteurized soil, however, seedborne Fusarium did not cause significant disease in seedlings. Biological control of seedborne Fusarium during stratification may be important both to reduce the contribution of seedborne Fusarium to nursery soil and to protect germinants from soilborne Fusarium. We hypothesized that Pseudomonas chlororaphis isolate RD31-3A, a fluorescent pseudomonad previously shown to control Fusarium on Douglas-fir, would reduce the spread of Fusarium during stratification and protect seedlings from damping-off when seeds were planted into soil infested with pathogenic F. oxysporum. High populations of RD31-3A were recovered from seeds after stratification, and bacterial treatment reduced the spread of Fusarium without affecting seed germination or subsequent seedling dry weights. RD31-3A did not, however, protect seedlings from soilborne F. oxysporum. Nevertheless, seed treatment with bacteria during stratification may be an efficient way to deliver biological control agents to conifer seeds. / Graduation date: 1997

Graduation date: 1966

Rhabdogloeum pseudotsugae Sydow has been suspected of being the imperfect stage of Rhabdocline pseudotsugae Sydow since their original description by Sydow in 1922. Because Rhabdogloeum has been reported so seldom in North America, and never in Europe, this possibility has been considered slight by most investigators. Investigation of the problem of Rhabdocline pseudotsugae in British Columbia revealed several new aspects of the association between the two leaf-cast diseases. Inspection of Rhabdocline and Rhabdogloeum collections from the interior of British Columbia indicated that the association of Rhabdogloeum pseudotsugae and Rhabdocline pseudotsugae is more prevalent than was formerly believed. Collections from the coast, and on Vancouver Island in particular, indicated that the association is probably less prevalent there than in the interior. In relation to the frequent and widespread occurrence of Rhabdocline throughout the Douglas fir range however, Rhabdogloeum is seldom found. If Rhabdogloeum pseudotsugae is the imperfect stage of Rhabdocline pseudotsugae, then it appears that frequently the Rhabdogloeum stage and occasionally the Rhabdocline stage is completely suppressed, as both stages have been found dissociated from each other. Frequent observation of a group of tagged Rhabdocline-infected trees on Vancouver Island over a period of two years did not reveal the presence of a Rhabdogloeum stage. Tissue cultures of lesions from these tagged trees, however, resulted in the growth of a fungus quite similar in appearance to that produced in tissue cultures by lesions typical of those produced by Rhabdogloeum pseudotsugae. This supports the view that Rhabdogloeum pseudotsugae is the imperfect stage of Rhabdocline pseudotsugae. Observation of these trees indicated that Rhabdocline pseudotsugae is capable of vegetating two years before producing apothecia. Apparently it is also capable of vegetating more than two years or of infecting leaves other than those of the current year. / Science, Faculty of / Botany, Department of / Graduate

A study was carried out to determine factors which influence the abundance of Adelges (Chermes) cooleyi Gill, on Douglas fir. This was done through the observation of populations in the field, supported by some laboratory work designed to show that certain influences are important. The work was done during the summer of 1960 in a young stand in Totem Park near Marine Drive and Agronomy Road on the U.B.C. campus, Vancouver. The following items were investigated: 1.) Inter tree differences, 2.) Intra tree variations, 3.) Population changes with time, 4.) Mortality of the insect. Abundance was affected by extrinsic influences on the trees, such as location and exposure and intrinsic factors such as time of bud opening and twig length. Within a tree the abundance of Adelges cooleyi was affected mostly by microclimatic factors, resulting in high abundance of the insect in the peripheral part of the lower crown. The average number of living insects decreased with time rectilinearly in generation 1 (Sexuparae and Progredientes) and logarithmically in generation 2 (Neosistens). A critical period during establishment of generation 2 caused the logarithmic changes. Mortality estimates by direct counts were subject to a large error because many of the dead insects fell off. / Forestry, Faculty of / Graduate

Saprophytic fungi and bacteria were recovered from healthy foliage of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). The populations of microorganisms on foliage were variable and changed through the growing season. Three species of the bacteria isolated from Douglas fir foliage were used in attempts to control the development of the rust, Melampsora medusae Thum., on Douglas fir seedlings in the greenhouse. Effective control was obtained when Bacillus cereus Frankland and Frankland and B. mycoides Flugge were applied to the seedlings in pure cultures of nutrient broth. The most effective control was obtained from the application of a mixture of these two species and a third unidentified species of Baci1lus in nutrient broth. Less effective control resulted from the application of bacteria suspended in water and cell free filtrates of the bacterial cultures. The numbers of bacteria on the foliage of Douglas fir were estimated using a modification of the soil dilution and bacterial plate count technique. The bacterial populations on foliage of Douglas fir in the greenhouse and in the field were increased by the application of bacteria in nutrient broth and sterile nutrient broth. / Science, Faculty of / Botany, Department of / Graduate

A hierarchical series of studies, based mainly on molecular data, was conducted to elucidate the life history of the Douglas-fir Swiss needle cast pathogen Phaeocryptopus gaeumannii at macro- and micro-evolutionary scales. This information was then utilized to design and evaluate molecular diagnostic tools for use in studies on the epidemiology of a Swiss needle cast outbreak near Tillamook, Oregon. Phylogenetic analyses of partial nuclear ribosomal gene sequences indicated that P. gaeumannii, currently classified in the Venturiaceae, is closely related to neither Phaeocryptopus nudus, type of the genus, nor Venturia inaequalis, type of the Venturiaceae. Instead, it is closely related to members of the "sooty molds" (Capnodiales), particularly the common and morphologically similar Douglas-fir epiphyte Rasutoria pseudotsugae (Euantennariaceae). Single-strand conformation polymorphisms, revealing DNA sequence variation in five loci, were used to investigate population biology of P. gaeumannii from a worldwide collection of isolates. In western Oregon, P. gaeumannii population structure suggests a predominantly selfing reproductive mode within two reproductively isolated sympatric lineages. One lineage was widely distributed both locally and abroad. The second lineage was restricted to western Oregon and suggested a correlation with symptoms of Swiss needle cast. A novel application of real-time PCR allowed species-specific detection and quantification of P. gaeumannii and proved a good measure of its biomass in Douglas-fir needles. Compared to other techniques (ergosterol and a DNA probe), real-time PCR correlated best with visual estimates of needle colonization and additionally proved useful early in the first year of the colonization process before visible development of fruiting structures. While all four methods provided evidence that sites expressing a range of disease severity differed in the degree of fungal colonization, only real-time PCR consistently separated both moderately and severely diseased sites from relatively healthy sites. Seedling inoculation experiments, fulfilling Koch's postulates, demonstrated that P. gaeumannii is the causal agent of Swiss needle cast, as observed in the Tillamook epidemic. Furthermore, the incorporation of virulence tests provided independent, non-molecular evidence that Oregon's pathogen population is not homogeneous. One strain, isolated from a severely diseased site, caused significantly greater symptom severity than strains derived from less damaged sites. / Graduation date: 2002

Bacterial galls on Douglas-fir (Pseudotsuga menzeisii [Mirb.] Franco), collected from the southern tip of Vancouver Island, the Greater Vancouver area and the Hope region of British Columbia, were generally globose in shape with rough, irregular surfaces and measured between 0.5 and 2.0 cm in diameter. The galls were generally located on the tips of branches or twigs of 10- to 20-year old Douglas-fir trees. The bacterial gall disease appeared to affect few Douglas-fir trees in the collection areas and bacterial galls were not found on any other coniferous species. Furthermore, there have been no reports of serious damage to natural forests in British Columbia due to bacterial gall disease. Young, greenhouse-grown Douglas-fir seedlings occasionally died if the tip of the main stem was artificially inoculated. Often new growing tips would be produced affecting the growth form of the seedlings. Two types of gall-forming Erwinia spp. were isolated from Douglas-fir galls. Typical isolates, tentatively identified by fatty acid analysis as Erwinia salicis, produced galls which were rough and irregular in shape composed of multiple outgrowths marked by a single or cross-shaped fissure. The atypical isolate, tentatively identified by fatty acid analysis as Erwinia herbicola subsp. herbicola, produced galls which were smooth and generally round in shape with the surface cracking as the gall expanded. Colonies of the typical isolates grown on casein-peptone-glucose media were characteristically round, slightly domed with somewhat concentric ridging observed near the margins of the colonies. Three to 4 day old colonies of the atypical isolates grown on casein-peptone-glucose media were characteristically round and concave while older colonies produced an extracellular slime and were more irregular in shape. In Luria Broth, the typical isolates grew at temperatures of up to 32°C while the atypical isolate grew at temperatures of up 34°C. The typical isolate was resistant to a wider range of antibiotics than the atypical isolate. Polyclonal antisera were produced against glutaraldehyde-fixed whole cells of both the typical T-2789 and atypical A-0181 gall-forming Erwinia isolates. The purified antisera were isolate specific as tested by immunodiffusion and an indirect ELISA against several different phytopathogenic bacteria including Pseudomonas syringae pv. syringae, Erwinia herbicola subsp. herbicola, Agrobacterium tumefaciens, Rhizobium leguminosarum and Erwinia carotovora subsp. carotovora. Plasmid profiles of the typical Erwinia isolates contained one band while the atypical isolate characteristically contained 4 to 5 bands which appeared to be different forms of at least one plasmid. Restriction digests of the typical isolates suggested a size of approximately 50 kb while complex digestion profiles were obtained for the atypical isolates because of the difficulty in isolating individual plasmid types. From visual estimates against Hindlll-digested lambda DNA, a size of between 10 and 20 kb was suggested for the fastest moving plasmid band of the atypical isolate. No homology was observed between the different plasmid types characteristic of the two isolates. The role of the plasmid DNA of the atypical isolate in pathogenesis was not determined because curing of the plasmid(s) was not successful using high temperature treatments plus chemical curing agents. Heat treatment experiments, in which the pathogen was selectively killed at various times after inoculation, demonstrated that the bacteria are required to be present for gall induction and continued development of the gall for both of the gall-forming Erwinia isolate types. Pathogenicity of the isolated bacteria was tested on 14 conifer species, other than Douglas-fir, including Abies, Chamaecyparis, Pinus and Thuja spp. The typical isolates were weakly pathogenic on Abies, Larix and Picea spp. The atypical isolate was weakly pathogenic on Abies, Chamaecyparis, Larix, Picea and Pinus spp. Due to the limited damage caused on the conifers tested and to their infrequent occurrence, these gall-forming pathogens do not appear to be of economic importance to the forestry industry. / Land and Food Systems, Faculty of / Graduate