parameters in largescale dissemination and landscape suitability in recent spread of white pine blis

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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
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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

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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
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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.
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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

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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
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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

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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
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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

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likelihood of transport
transport unlikely
transport likely

• likelihood ranked 1-4 (1low, 4very high)
• persistence of conditions is important
• 18-hour moving average
• yields a likelihood of transport calendar

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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

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very high transport likelihood summer Trough

• most frequent May - August
• present in all months

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low transport likelihood summer
Trough-Ridge-Trough (northerly displacement)

• most frequent in August
• present in all months

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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

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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

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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 (1low, 4very high)

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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 6very high, 5.1-6high,
  4-5moderate,
• 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

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likelihood of infection Sacramento
Mountains 1972 spore season
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very high infection likelihoods

• AprilJuly, 19651974
• 4880 observations
• thirty three observations (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

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June 1-15, 1969 most likely for infection
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verification of the model

• consider other sites in the western U.S. that are
  susceptible to infection
• expand the study period to include the 19751990
  spore seasons
• compare the likelihood of infection at these
  sites with the the Sacramento Mountains

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map of target points
White pine reported WPBR reported complied by
B.W. Geils, June 2006
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likelihood of infection upper-level and surface
components 1 Apr31 Jul 19751990
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likelihood of infection 1 Apr31 Jul 19751990
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likelihood of infection 1 Apr31 Jul 19751990
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likelihood of infection 1 Apr31 Jul 19751990
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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

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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