Dissemination and Landscape Suitability of White Pine Blister Rust in North America

1. parameters in large-scale dissemination and landscape suitability in recent spread of white pine blister rust in North America Katrina Frank Center for Climatic Research Department of Geography University of Delaware

2. goal of the project • identify the coincidence of upper level and surface meteorological conditions conducive to Cronartium ribicola, white pine blister rust, infection at susceptible sites in the western U.S. • compare the likelihood of infection at these sites with the certainty of infection at the Sacramento Mountains

3. WPBR in the western U.S. • initial introduction • 1910 at Point Grey, British Columbia • near Vancouver • infected seedling imported from France • WPBR discovered in 1921 • spread incrementally • within three years had spread 120 miles WPBR observed in 1913 point of introduction, 1910 infected sites, 1913 ~ Mielke, 1943

4. WPBR in the western U.S. WPBR observed in 2002 • spread incrementally • reached southern extent of white pine and Ribes range in the Sierra Nevada in the early 1960s • disjunction • cankers found in south central New Mexico in 1990 • date to around 1970 ~ Vogler, unpub.

5. disjunct WPBR population • WPBR was spread to the Sacramento Mountains by a discrete atmospheric transport event • appeared simultaneously at several distinct locations at same elevation • rust is genetically identical to that found in southern Sierra Nevada • no transplantation of trees ocurred in the area • initially appeared far from settlement in the region • ~ (Hawksworth, 1990; Van Arsdel et al., 1998; Hamelin et al., 2000) • transport of WPBR over long distance indicates potential for further spread by the same means

6. important facts about WPBR • requires two hosts • white pine tree Pinus Strobus • bush of the genus Ribes • currants and gooseberries (cultivated and wild) • spread from host to host by the wind • requires moisture to take hold in an area R. hudsonianum - northern black currant

7. life cycle of WPBR • host A - white pine tree • 3-4 years from initial infection to spread • aceiospores spores released in spring, early summer • can travel long distances • viable 5-7 days • durable • host B - Ribes bush • infected in spring, early summer • rust spreads to nearby trees in fall - before leaves drop • basidiospores can travel only short distances • viable for short periods • fragile

8. life cycle of WPBR long-distance transport may occur basidiospore infects pine tree telia appear on Ribes canker begins to produce aceiospores basidiospore infects pine tree uredia appear on Ribes pycinia appear on pine bark begins to show discoloration

9. how to study the spread of WPBR • synoptic indexing of upper level flow patterns • provides a simple way to summarize the combination of variables working together at a given time • identify periods when upper level flow was conducive for transport of spores from source to target • coupling with surface observations • eliminate days when infection was unlikely, even under favorable upper level flow conditions • this approach allows understanding of the climatology of spread as opposed to exploring a specific occurrence

10. likelihood of transport transport unlikely transport likely • likelihood ranked 1-4 (1=‘low’, 4=‘very high’) • persistence of conditions is important • 18-hour moving average • yields a ‘likelihood of transport’ calendar

11. Upper Level Synoptic Index • 4x daily observations at 500mb • geopotential height • specific humidity • u-wind component • v-wind component • cluster analysis • results in 16 clusters typifying upper level flow patterns

12. very high transport likelihood summer Trough • most frequent May - August • present in all months

13. low transport likelihood summer Trough-Ridge-Trough (northerly displacement) • most frequent in August • present in all months

14. likelihood of germination • necessary conditions for WPBR to germinate • period of 6 hours or more with saturated air at the Ribes leaf and air temperatures above 13 °C • must occur within three weeks of favorable upper level conditions

15. likelihood of germination • considered surface conditions for 21 days following each observation • employed third-degree polynomial to weight longer, less frequent events more heavily • inverse, linear weighting to account for time elapsed between potential transport and surface conditions • results in one ‘likelihood of germination’ value for the 21-day period following each observation

16. likelihood of germination • surface values for each observation placed in likelihood classes • values greater than four standard deviations - ‘very high’ likelihood for germination • values two to four standard deviations - ‘high’ likelihood for germination • values greater than zero but less than two standard deviations - ‘moderate’ likelihood for germination • observations with no favorable surface conditions - ‘low’ likelihood for germination • classes ranked 1-4 (1=‘low’, 4=‘very high’)

17. coupling upper level and surface conditions • sum likelihood values for each observation • result is a ‘likelihood of infection’ value • range 2-8 • label resulting values • initial thresholds: >6=‘very high’, 5.1-6=‘high’, 4-5=‘moderate’,<4=‘low’ • a value of 6 could result from the sum of a ‘very high’ and a ‘moderate’ • sensitivity testing showed that thresholds of 6.1, 5.1 and 4.1 were more appropriate • create ‘likelihood of infection’ calendar

18. ‘likelihood of infection’ Sacramento Mountains 1972 spore season

19. ‘very high’ infection likelihoods • April–July, 1965–1974 • 4880 observations • thirty three observations (<1%) fell in this category • 1972 - 1 • 1971 - 2 consecutive • 1968 - 7 during the week of 1 July • 1969 - 23 in the first two weeks of June • three periods of 24 hours or longer

20. June 1-15, 1969 most likely for infection

21. verification of the model • consider other sites in the western U.S. that are susceptible to infection • expand the study period to include the 1975–1990 spore seasons • compare the likelihood of infection at these sites with the the Sacramento Mountains

22. map of target points White pine reported WPBR reported complied by B.W. Geils, June 2006

23. likelihood of infection upper-level and surface components 1 Apr–31 Jul 1975–1990

24. likelihood of infection 1 Apr–31 Jul 1975–1990

25. likelihood of infection 1 Apr–31 Jul 1975–1990

26. likelihood of infection 1 Apr–31 Jul 1975–1990

27. directions for future work • other white pine populations are susceptible to WPBR spread by the same means • expand the map to include white pine populations in Mexico • field studies continue to generate new information about populations’ WPBR status • add information about surface conditions at the source to refine the model • apply this methodology to the spread of other pathogens, even insects

28. acknowledgements collaborators: Brian W. Geils - USDA Forest Service, Rocky Mountain Research Station Harold W. Thistle, Jr. - USDA Forest Service, Forest Health Technology Enterprise Team Laurence S. Kalkstein - Center for Climatic Research, Department of Geography, University of Delaware funded by: USDA Forest Service cooperative agreement award number 01-CA-11244225-231