The role of climate and topography in the development of Dothistroma septosporum. Crystal Braun, Kathy Lewis and Alex Woods.

Transcription

1 The role of climate and topography in the development of Dothistroma septosporum. Crystal Braun, Kathy Lewis and Alex Woods February 8, 2008

2 Outline Introduction Study 1: Effects of Climate Study 2: Effects of Topography Results Summary

3 Introduction Dothistroma septosporum (Dorog.) Morelet Affects two-, three-, and five-needle pines. Characterized by red banding, caused by the toxin dothistromin. Two stages: asexual conidia sexual ascospores Infection starts in base of crown and works up. Causes premature defoliation of 1-yr and current year needles. New needles generally resistant. Severe case of young pine (~10 yrs) infected with D. septosporum. Photo taken by Crystal Braun.

4 Introduction Recognized internationally as problematic pest, affecting over 60 Pinus species in 45 counties. First recorded incidence of Dothistroma needle blight in northwestern British Columbia's Kispiox Forest occurred in the early 1960s. Dendrochronology records show outbreaks go back as far as the early 1800s aerial surveys of 40,898 ha of pine plantations found that 92% of showed signs of Dothistroma infection (Woods et al. 2005). 9% of pine plantations so severely defoliated that recovery seems unlikely (Woods et al. 2005) Severity of current epidemic unprecedented. Figure 1: Skeena Stikine Forest Region, encompassing Smithers and Hazleton. Borrowed from the Province of British Columbia. m

5 Climate Influence of climate seen with other diseases, such as Swiss Needle Cast (Rosso & Hansen 2003; Manter et al. 2003). D. septosporum conidia are usually dispersed by rainsplash, though there is some evidence of conidial dispersal by wind and cloud transport (Bradshaw 2004). Gadgil (1977) found that the majority of conidia were released during periods of rain or heavy mist when infected foliage was dripping wet (in lab). Spatial correlation between the area subjected to increased MSP (mean summer precipitation) and the area affected by the current Dothistroma epidemic is striking (Woods 2003). Warm, moist summers and cool, wet falls are thought to be contributing climatic factors to the severity of the outbreak (Woods 2003).

6 Frequency of Sexual Stage Generally the sexual stage of fungi causing needle disease is uncommon (Harrington & Wingfield 1998). Funk (1979) observed the sexual stage 4-5% of the time when monitoring infection of new needles in both dry and wet conditions. Peterson (1973) monitored Dothistroma development and spore production and reported having never observed the sexual stage. The importance of conidia may be greater than ascospores as they are dispersed over a longer period (Karadzic 1989); however the importance of the ascospores in the life cycle of the fungus is unknown at this time. Sexual reproduction facilitates genetic recombination, which may give rise to more virulent strains of the disease. Its appearance in high frequencies may help explain the severity of the current outbreak. High levels of genetic variability observed (Dale 2008).

7 Topography Influence of topography seen with other diseases: Sirococcus shoot blight (Anglberger & Halmschlager 2003) Dogwood anthracnose (Windham et al. 1993) Swiss Needle Cast (Rosso & Hansen 2003; Manter et al. 2003) In a mixed stand, infection of P. attenuata was found to be less severe than P. radiata. Possible role of microclimatic conditions suggested by Cobb & Miller (1968), as P. attenuata was planted on a slope above the other pines. If D. septosporum conidia are transported by periods of heavy fog then it is likely to expect areas with severe infection in places where cooling air collects. Marks & Hepworth (1986) found hot spots for D. septosporum infection were in depressions, shallow gullies, and flat land; whereas trees in path of freely draining cool air showed only very light infection.

8 Proximity to Water Bodies Transport of D. septosporum conidia passively through water droplets has been noted in previous literature (Bradshaw 2004; Ivory 1972). Gadgil (1974) found that infection severity was higher and the prereproductive period was shorter in foliage kept continuously wet than when it was kept wet for 8, 24, or 48 hours after inoculation. Heavy fogs generated in low-lying pine plantations in close or immediate proximity to rivers, lakes, or streams may facilitate D. septosporum development and thereby contribute to disease severity and intensity.

9 Study 1: Effects of Climate How do temperature, relative humidity, and leaf wetness influence the development and expression of Dothistroma? How frequent is the sexual stage of Dothistroma in northwestern BC?

10 Study 1: Methods Plot monitoring: 12 plots in Bulkley, Kispiox, and Cranberry TSAs In each plot, 6 trees flagged 4 nodes/tree 6-10 needles/node Hobo weather stations in plot center Weekly Observations (June through September 2007) : Red banding and fruiting body development. Spore production assessed by vial dipping and hemocytometer counting (trials with volumetric spore traps and spore capturing found to be unreliable). When fruiting bodies detected, sample taken for needle dissection to determine the ratio of stromata (asexual) to ascoma (sexual). 280 samples of 10 each D. septosporum fruiting bodies visible on needle surface. Photo taken by Crystal Braun.

11 Study 2: Effects of Topography How do site factors (e.g. elevation, slope, slope position, aspect) influence disease intensity? Does proximity to major water bodies have an effect on disease severity, and can this be explained by temperature and relative humidity requirements for Dothistroma production and release?

12 Study 2: Methods Aerial survey data from Dothistroma monitoring program: Covers Bulkley, Cranberry, Kalum, Kispiox, and Nass TSAs. 607 openings assessed. Dothistroma infection assessed as a measure of functional live crown. Site effects evaluated: elevation, slope, aspect, proximity to major water bodies. Distribution of plot data. Image generated by Crystal Braun.

13 Results Spore counting: Conidia production detected July 27 - August 29. Ascospores never detected. Fruiting body dissection: Stromata abundant. Ascoma (sexual fruiting bodies) confirmed in 2/280 needle samples August 9 and September 16. Weekly observations insufficient for monitoring sexual stage?

14 25 20 Temperature ( o C) Temperature (C) Jun 2-Jul 2-Aug 2-Sep Relative humidity (%) Jun 2-Jul 2-Aug 2-Sep Fruitingbodyproductionper needle Fruiting body production per needle Fruiting body production per needle Relativehumidity(%) Fruiting body production per needle

15 25 20 Temperature ( o C) Temperature (C) Jun 2-Jul 2-Aug 2-Sep Relative humidity (%) Conidia (spores\ml) Relative humidity (%) Conidia (spores\ml) 1-Jun 2-Jul 2-Aug 2-Sep Conidia (spores\ml)

16 Results Preliminary analysis of aerial survey data found significant effects of elevation and slope on functional live crown (F 2, 604 = 60.98, p = <0.0001). Multiple R2: Adjusted R2: Aspect and proximity to major water bodies do not appear to have a significant influence on disease development. Data analysis currently underway.

17 Summary Want to know what climate and site conditions are contributing to disease development (with respect to the outbreak here in BC) and influencing disease expression. Working on a hazard rating system of pine plantations to future Dothistroma outbreaks that is adaptable to predictions of climate change. Data analysis currently underway.

18 Acknowledgements Brian Aukema (CFS) Alex Woods, MOF (Smithers, BC) Skeena Stikine Forest District (Hazleton Office) UNBC - the dendrochronology lab and GIS lab Field assistants Chris Konchalski and Dylan Richards

19 Extras Preliminary design of slide setup for spore trapping. Photo taken by Crystal Braun. stromata Volumetric spore trap (Gadoury & MacHardy 1983). Life cycle of D. septosporum. Adopted from Funk (1985). Severe case of young pine (~10 yrs) infected with D. septosporum. Photo taken by Crystal Braun. Snapshot of roadside pine infected with D. septosporum taken in the Kispiox TSR, north of Hazleton, BC. Photo taken by Crystal Braun.