A disease, causing severe flagging of young western white pine (Pinus monticola Dougl.), was investigated at Hill Siding and Arrow Park, British Columbia. The primary symptom of the disease was flagging of twigs, resulting from a rapid necrosis of terminal shoots and less commonly from girdling-lesions on 2-year-old growth. A small percentage of the severely flagged trees died. Damaging effects of the disease were confined to trees under 40 years of age and to stand forms with a higher than average component of white pine in the susceptible age class. Efforts to isolate the causal fungus yielded 22 fungi in culture, only two of which occurred with sufficient frequency to warrant further study, an unknown fungus "B” and Pullularia pullulans (deBary) Berkhout. A search for fructifications associated with the disease revealed apothecia of a Tympanis, very similar to those of Tympanis pithya (Karst.) Karst., to be associated with 16 per cent of a random sample of 425 flagged twigs. The pycnidia of the imperfect stage of Tympanis sp. occurred less commonly. Spore cultures from Tympanis apothecia were different from those of any of the 22 fungi isolated in tissue culture and it seemed probable that Tympanis occurred as a pioneer saprophyte on killed twigs. External signs of Pullularia pullulans occurred commonly in the form of erumpent sclerotia, and external hyphae with resting spores. A scale insect, resembling Matsucoccus sp., was found at a high infestation level in one stand and less commonly in the remaining stands. Reasons for discounting the insect as a primary causal agent of flagging are outlined. Field inoculations with Pullularia pullulans and greenhouse inoculations with Pullularia pullulans and the unknown fungus "B" produced questionable results with the latter fungus, but indicated Pullularia pullulans to be pathogenic under the conditions imposed by the experiment. Results of inoculation experiments are snmmarized in four tables. The historical background and cultural description of Pullularia pullulans is outlined. Experimental and observational evidence suggests that the fungus is one of the causal agents, and probably the primary agent for the flagging. On the basis of the limited damage caused by the flagging and the sporadic occurrence of the susceptible stand form, control measures are deemed unwarranted. / Forestry, Faculty of / Graduate

The objectives of this study were to define the life history of the lodgepole terminal weevil (Pissodes terminalis Hopping) in the Cariboo Forest Region, to quantify the magnitude of damage resulting from weevil attacks, and to determine if P. terminalis activity was associated with measurable tree and stand parameters such as leader dimensions and density. Four study plots in juvenile lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands near Riske Creek, B. C. were selected to provide data on the biology of the lodgepole terminal weevil. In each plot, weekly collections of 10 weevil-attacked terminal shoots were made from June 3 to August 29, 1980, and monthly collections were taken during September through November. All leaders were dissected and the numbers of each P. terminalis life stage and associated predators/parasitiods were recorded. Seventy-one survey plots in lodgepole pine stands between 8 and 29 years of age throughout the Cariboo Forest Region were assessed for weevil activity. Each survey plot contained 25 trees over 2 metres in height, and each tree was measured for height, diameter at breast height, leader length, and basal leader diameter. Stand age, elevation, density, and all weevil attacks (including year of attack and type of resultant stem deformity) were also recorded. Weevil development appeared to be fairly uniform regardless of stand density and/or elevation; therefore, the data from all four biology study plots were combined to construct a life history diagram. In 46% of the survey plots one or both of the leader dimensions was significantly greater for attacked trees as compared to unattacked trees. In 28% of the plots attacked trees were either significantly taller or larger in diameter. Over 50% of the trees in stands of less than 4,000 stems per hectare had been attacked by P. terminalis at least once. Severe stem deformities such as forks and "stag-heads" comprised a larger proportion of damaged trees in the lower stand density classes. Weevil activity appeared to be higher in 1980 than in 1979. It was concluded that the lodgepole terminal weevil is currently a widely distributed and serious pest of young lodgepole pine stands in the Cariboo Forest Region. Given the present levels of weevil-caused damage as well as the possibility of future attacks, it was recommended that the activity of P. terminalis be considered when silvicultural practices such as juvenile spacing are undertaken in these stands. / Forestry, Faculty of / Graduate

No description available.

Call number: LD2668 .T4 1979 H64 / Master of Science

No description available.

The distribution, population ecology, behavior and host interactions of the root weevil, Hylobius warreni Wood were investigated in lodgepole pine forests in Alberta. Highest incidence of the weevil occurs in the Lower Foothills Section of the Boreal Forest Region, between 2,500 and 4,000 feet in elevation. In even-aged forests weevil numbers are distributed according to stand maturity, stand density, tree size and duff depth. Interactions between these variables modify the patterns of abundance in different stands. Attack incidence upon the host varies, being highest in the collar zone and least on lateral roots. As tree size increases the ratio of weevils on roots/weevils on collar tends to increase. During normal stand development initial invasion of weevils occurs at age 6-10 years, and persists with successive attacks throughout the life of the stand. Weevil populations are highly aggregated in mature stands; "k" values of the negative binomial varied from 0.09 to 0.68, while Taylor's power law gave an aggregation index "b" value of 1.92. Estimates of weevil populations indicated that low levels are characteristic of this species and are maintained, mostly within the range 200-1200 weevils per acre. Estimates of absolute numbers indicate similar levels of abundance occur in young and old stands alike, while population intensity values increase with stand maturity. The highest rate of increase of attack density per tree appears to occur during the ages of 30-45 years. The structure of weevil populations was described and mortality factors were identified and measured for larval, pupal and teneral stages. The main mortality factor of these stages appeared to be from excess moisture in the larval gallery and pupal cell. Only the first 3 larval instars are definable by head capsule width measurement. The feeding behavior of larvae varies with its maturity. In the early instars the feeding pattern relates to bark thickness, but damage is insignificant. Damage of late instars may consist of decorticated gallery lengths up to 24 cm. Larval and pupal habitats are described to indicate the special adaptations for survival. Adults live at least 3 years but lay their eggs during the second and third summers of adulthood. Their seasonal peak of activity occurs in June and early July. Dispersion in the forest tends to be random, commencing about 2 hours after sunset and when temperatures exceed 36-40 °F. Host trees are located partly by vision, the pattern of selection being related to host size. Maximum fecundity per female per season may be 36 or more eggs, but in the field the actual number may not exceed 12.0. Most eggs are deposited singly in niches excavated by the female in the root-collar bark, and are subsequently covered over with excreta. The egg requires a moist environment maintained for up to 42 days for successful hatch. During stand development up to 100 percent of trees may sustain larval feeding damage accumulated to various degrees of intensity. Young trees up to 30 years of age show less resistance to girdling damage than older trees, and reasons are given for this. Estimates of mean height losses of 20-25-year old tree stems sustaining 50 percent girdling were 11.5 and 10.9 percent over 2- and 3-year periods respectively. The total impact of the weevil in the stand as a whole appears to hasten successional changes during stand development. A method of regulation of weevil abundance is postulated and takes into account the behavior of the female during oviposition, host selection, larval feeding habits, cumulative damage and host interactions. Overall numerical restraint and stability of numbers are considered to be effected largely through the inherent behavior of adults. Several weevil control measures are suggested through forest management. Clearcutting of mature timber in alternate strips reduced a weevil population by an estimated 67 percent, but some larvae developed to adults in the cut stumps one and two years after tree removal. The effect of cutting resulted in a concentration of weevils on adjacent trees along stand peripheries, 3-5 years after cutting. / Forestry, Faculty of / Graduate

Dwarf mistletoes are Parasitic flowering plants that infect conifer tree species. The effects of Arceuthobium americanum on the seed crop of Pinus contorta were examined over a two year period to evaluate the effects of altered host reproductive success on host population dynamics. Heavily infected trees produced significantly fewer cones than uninfected trees during the first season in which cones were collected. Cone length, number of seeds per cone, individual seed mass, and total calories per seed were significantly reduced in moderately and heavily infected trees. Trees with different levels of infection showed trends consistent with the above but no significant differences were observed during the second season. The number of seeds that were produced, disseminated, and that germinated per square meter of forest floor was significantly less in heavily infected plots than in lightly infected plots. Survival of one year old seedlings, however, was significantly higher in heavily infected plots. Significant increases in the abundance of woody litter due to increases in mortality of mature trees and witches brooms were positively correlated with increases in seedling survival in heavily infected plots. Survival of trees less than 45 years of age also increased as the level of infection in plots increased. This increases the fraction of total density that saplings represent in heavily infected stands. The total basal area of plots with different levels of infection were uniform, implying that all available environmental resources are being utilized. The differences in age distribution between lightly and heavily infected plots, however, indicate that resources are partitioned differently between saplings and mature trees in plots with different levels of infection. Dominant host trees experienced higher mortality in heavily infected plots than in lightly infected plots. This reduces the total biomass of all mature trees. Increased mortality of dominant host trees frees resources which reduces intraspecific competition thereby contributing to increased sapling survival in heavily infected plots. Consequently, stand density increases as the level of infection increases.

No description available.

No description available.

No description available.