Forest Investment Account (FIA) - Forest Science Program
FIA Project Y073204

    Relationships between climate, forest practices and incidence of Dothistroma needle blight septosporum
Project lead: Lewis, Kathy
Author: Lewis, Kathy J.
Imprint: [Prince George, B.C.] : [University of Northern British Columbia], 2007
Subject: Forest Investment Account (FIA), Dothistroma Pini, Dothistroma Pini, effect of climate on, Pinus, Diseases and Pests, Vegetation and Climate, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Red band needle blight is an economically important forest disease which causes serious defoliation of many coniferous trees, particularly pine when planted out of their native range (Bradshaw 2004). The fungus responsible for the disease, Dothistroma septospora (Dorog.) Morelet infects the needles, leading to necrotic lesions, needle death and reduced wood yield. Premature defoliation caused by this fungus has resulted in complete failure of many exotic pine plantations in New Zealand, South Africa and South America. Monterey pine plantations on the west coast of North America have also been severely damaged, but the disease is not found in natural stands of this species (Patton 1997), and until recently has been uncommon and little concern in natural stands of other hard pine species of western North America. An outbreak of Dothistroma is taking place in the Interior Cedar Hemlock zone (ICH) east of the coast range in northern British Columbia where climate is characterized by a warm and humid coastal weather system. Disease development and subsequent effects are highly dependent on weather conditions. The current outbreak in northwestern British Columbia is thought to be due in part to weather patterns that have become more conductive to the spread of the fungus: mild summer temperatures and prolonged periods of high humidity or leaf surface water films. Results of both ground and aerial surveys have shown successive increases in the extent and severity of the Dothistroma epidemic in lodgepole pine-leading stands. Evidence of 55-year-old natural stands of lodgepole pine during the survey were also observed to have >20% tree mortality as a result of Dothistroma (Woods 2003). Dothistroma poses a significant threat to the growth and yield of lodgepole pine in northwestern British Columbia. The current outbreak in British Columbia is much larger than what has been observed in the recorded past. Weather in the past decade appear to be changing resulting in frequent episodes of warm rain during summer months. In order to avoid future epidemics, and to develop comprehensive strategies for management of lodgepole pine, it is critical that the impacts of climate and weather patterns on disease severity of Dothistroma are understood. This project fits with latest strategic goals of the Forest Sciences Program, specifically in the Program: Timber Growth and Value, and the Theme: Timber Losses to Environmental Factors. The main objective of this project is to determine the influence of weather patterns on the extent and nature of current and historic disease severity to understand the spatial and temporal variations of the outbreaks. A second objective is to analyze the distribution of current and past disease outbreaks with respect to changes in host abundance due to forest management. Methods: Spore traps and simple weather stations will be identified or established in approximately 10 locations in the Interior Cedar Hemlock (ICH) zone and the Sub-boreal Spruce zone (SBS) within the affected area. These will be monitored on a regular basis to determine weather conditions that are conducive to spore production. Documented past outbreaks of D. septospora will be used to develop a dendrochronological signal that can be used to look back in time through the tree-ring record, in order to identify pre-record defoliation events. Climate reconstruction will be used to determine pre-record weather conditions and these will be correlated with past outbreaks. Within the region currently affected by Dothistroma, approximately 30 sites in northwestern British Columbia will be studied. Half of the study sites will be used to reconstruct and compare historic outbreaks of Dothistroma and historic climate. The remaining half will be used to study the influence of local weather patterns on current disease severity as it varies with topographic features. Sites for dendrochronological analyses will be selected based on the following criteria: <30km from a weather station, symptoms of Dothistroma, trees >15cm DBH, and >30 years of age. A total of 20 live host (pine) and 20 non-host (spruce) increment cores will be taken from each forest patch. Pine and spruce pairs will be selected for sampling based on evidence of longevity. One increment core per tree will be taken at 0.3m above the ground from both live and dead trees. Disks will also be sampled at 0.3m from selected sites. Stand data will be recorded, including percent species composition and DBH for all trees cored. All cores will be processed following the procedures of Stokes and Smiley (1968). Annual rings-widths will be measured to the nearest 0.001mm using the Velmex 'TA' System in conjunction with MeasureJ2X (1999-2004). Live and dead materials from each site will be cross-dated using the computer program COFECHA. This technique is use to detect measurement and cross-dating errors. The program ARSTAN (Cook and Holmes 1984) will be used to produce a master chronology for each species within each site. By comparing the tree-ring chronologies between the species, variations of shared factors such as climate can be removed ('corrected'), and periods of reduced growth can be inferred as periods of a disturbance. Identified outbreaks, as determined from the Forest Insect and Disease survey (FIDS) will be used to verify the dendrochronological signal. Other standardization techniques will be used to develop a climate-based chronology, and cross-referenced with weather records, provided by the Fire Centre in Smithers. Average monthly climatic values, and seasonal climatic values will first be correlated with identified outbreak periods as determined from FIDS records, then extended back in the tree-ring record to determine if climate is related to outbreak frequency and intensity. To determine the influence of local weather patterns on current disease severity of Dothistroma as it varies with topographic features, lodgepole pine plantations in the ICH will be selected within an age-class range of 15-20 years. Stand measurements will be collected on two scales according to meteorological conditions: (1) a meso scale that is determined by elevation, stand slopes and aspect, and (2) a micro scale that is determined by stand structure. Since hills, slopes, and valleys affect air drainage, and crown cover affect radiation patterns they are important influences of local weather. Severe Dothistroma infections in Pinus radiata plantations in California have been noted at a lower slope gradient than those trees at higher slope gradients (Bingham et al. 1971). As a result, authors attributed the differences in the degree of infection to microclimatic conditions rather than to host resistance. Therefore areas at lower slopes that receive longer periods of moisture throughout the day may be 'hot spots' of disease severity and may be centers of disease spread. To determine the natural spatial variations of the disease, a composite rating system specific to Dothistroma will be developed to characterize stand-level differences in disease severity. Included in the rating system will be an examination of annual radial growth using destructive sampling methods. The situation in British Columbia is clearly unique. Dothistroma is considered a serious forest pathogen in only exotic plantations of the southern hemisphere. However, the damage being reported in British Columbia is an example of disease severity in the northern hemisphere, in areas where the host is native, and mature stands are affected. A better understanding of the epidemiology of Dothistroma will help recognize high-risk situations and aid in the development of management practices to prevent future outbreaks. This research directly contributes to the topic of silviculture systems and treatments to control risks from forest pests.
Related projects:  FSP_Y051204FSP_Y062204
Contact: Lewis, Kathy, (250) 960-6659,


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Updated August 16, 2010 

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