parameters in large-scale dissemination and landscape

suitability in recent spread of white pine blister rust in

North America

Katrina FrankCenter for Climatic Research

Department of GeographyUniversity of Delaware

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

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

~ Mielke, 1943

WPBR observed in 1913

point of introduction, 1910

infected sites, 1913

WPBR in the western U.S. •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

WPBR observed in 2002

~ Vogler, unpub.

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

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

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

life cycle of WPBRtelia appear on Ribes

uredia appear on Ribes

basidiospore infects pine tree

basidiospore infects pine tree

canker begins to produce

aceiospores

pycinia appear on pine

bark begins to show discoloration

long-distance transport may occur

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

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

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

very high transport likelihoodsummer Trough

•most frequent May - August•present in all months

low transport likelihoodsummer Trough-Ridge-Trough

(northerly displacement)

•most frequent in August•present in all months

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

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

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’)

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

‘likelihood of infection’Sacramento Mountains

1972 spore season

‘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

June 1-15, 1969most likely for infection

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

White pine reported WPBR reported

complied by B.W. Geils, June 2006

map of target points

likelihood of infectionupper-level and surface components

1 Apr–31 Jul 1975–1990

class occurrences percent class occurrences percentLow 5451 69.81% Low 5110 65.45%Moderate 772 9.89% Moderate 2058 26.36%High 1137 14.56% High 217 2.78%Very High 448 5.74% Very High 422 5.40%

class occurrences percent class occurrences percentLow 4907 62.85% Low 6590 84.40%Moderate 1242 15.91% Moderate 1115 14.28%High 604 7.74% High 66 0.85%Very High 1055 13.51% Very High 36 0.46%

class occurrences percent class occurrences percentLow 0 0.00% Low 7708 98.72%Moderate 1209 15.48% Moderate 99 1.27%High 3430 43.93% High 0 0.00%Very High 3169 40.59% Very High 0 0.00%

Elko, NV

Sacramento Mountains, NM

Surface

Upper Level Surface

Sangre de Cristo Mountains, COUpper Level Surface

Upper Level

class occurrences percent class occurrences percentLow 3762 48.18% Low 7517 96.27%Moderate 2312 29.61% Moderate 212 2.72%High 396 5.07% High 33 0.42%Very High 1338 17.14% Very High 45 0.58%

class occurrences percent class occurrences percentLow 4816 61.68% Low 7641 97.86%Moderate 1827 23.40% Moderate 105 1.34%High 1165 14.92% High 35 0.45%Very High 0 0.00% Very High 26 0.33%

class occurrences percent class occurrences percentLow 3675 47.07% Low 7778 99.62%Moderate 1920 24.59% Moderate 29 0.37%High 437 5.60% High 0 0.00%Very High 1776 22.75% Very High 0 0.00%

Zion National Park, UT

Flagstaff, AZ

Mount Charleston, NV

Upper Level Surface

Upper Level Surface

Upper Level Surface

likelihood of infection1 Apr–31 Jul 1975–1990

class occurrences percent class occurrences percentLow 6579 84.26% Low 6243 79.96%Moderate 919 11.77% Moderate 1565 20.04%High 185 2.37% High 0 0.00%Very High 125 1.60% Very High 0 0.00%

class occurrences percent class occurrences percentLow 6544 83.81% Low 7782 99.67%Moderate 1223 15.66% Moderate 26 0.33%High 41 0.53% High 0 0.00%Very High 0 0.00% Very High 0 0.00%

class occurrences percent class occurrences percentLow 4188 53.64% Low 5837 74.76%Moderate 3611 46.25% Moderate 1971 25.24%High 9 0.12% High 0 0.00%Very High 0 0.00% Very High 0 0.00%

Elko, NV (1)

Zion National Park, UT (2)

Flagstaff, AZ (9)

Mount Charleston, NV (8)

Sacramento Mountains, NM (15)

Sangre de Cristo Mountains, CO (7)37.5ºN, 105ºW 35ºN, 112.5ºW

40ºN, 115ºW 35ºN, 115ºW

32.5ºN, 105ºW 37.5ºN, 112.5ºW

likelihood of infection1 Apr–31 Jul 1975–1990

likelihood of infection1 Apr–31 Jul 1975–1990

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

acknowledgementscollaborators:Brian W. Geils - USDA Forest Service,

Rocky Mountain Research StationHarold W. Thistle, Jr. - USDA Forest Service,

Forest Health Technology Enterprise TeamLaurence 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