Spruce Budworm (Tordeuse des bourgeons de l'epinette) at Bonanza Creek LTER: A clear case of temperature thresholds in a warming climate Glenn Patrick Juday, Professor of Forest Ecology Skeeter Werner, USDA FS, PNW Research Station (retired) Robert A. Ott, consultant ? Jim Kruse, USDA Forest Service S&PF

Large total area burned - early start to fire season - multiple simultaneous fires - large fires - lack of mid-summer “season-ending precipitation event” - active late fire season - continued vigorous spread - some fires extinguished by first snows of season - smouldering through the winter Spruce budworm reproduction/outbreak? Spruce budworm reproduction/outbreak? Strong negative tree growth anomaly of “negative responders” - w. spruce on low-elevation productive sites central AK - w. spruce (42%) at treeline Decrease in open water/lake surface area WARM TEMPERATURE ANOMALIES IN BOREAL ALASKA : Spruce bark beetle outbreak behavior in southcentral Alaska - shift from 2-yr. to 1-yr. life cycle

Photo: Paul Renschen

Photo: Robert A. Ott Spruce Budworm, Choristoneura fumiferana

PART 1. IT’S A BIG DEAL. IT MATTERS.

MacLean, D.A., Porter, K.B., MacKinnon, W.E., Beaton, K.P Spruce budworm decision support system: lessons learned in development and implementation. Computers and Electronics in Agriculture 27: 293 – 314. Power, J.M., National data on forest pest damage. In: Brand, D.G. (Ed.), Canada’s Timber Resources. Can. For. Serv., Petawawa National Forestry Inst., Chalk River, ON. Inf. Rep. PI-X-101. pp. 119–129. Spruce budworm outbreaks: Natural disturbance system - especially in NE North America Cause large-scale mortality of spruce and balsam fir - uncertainty in future forest structure and productivity The most destructive forest pest in Canada; The most destructive forest pest in Canada; - causes ~ 40% of the 81–107 million m 3 of timber volume lost to insects and disease each year. volume lost to insects and disease each year. Three major spruce budworm outbreaks in the 20th century; - beginning 1910, 1940, and 1970, - maximum extents of 11, 25, and 58 million hectares - late 20th century in northwest Canada (Alaska)

Budworm populations: Usually regulated by combinations of several natural factors - insect parasites - vertebrate predators - invertebrate predators, - adverse weather conditions. During prolonged outbreaks - stands heavily defoliated; eventually budworm starvation becomes important mortality factor.

Explaining spruce budworm outbreak behavior: a popular pastime Theory 1. The catastrophe theory of budworm outbreaks holds that major infestations occur every years, as the result of a cusp-catastrophe event, whereby populations jump suddenly from endemic to epidemic levels. Theory 2. Outbreaks are the result of spatially synchronized population oscillations that are caused by delayed density- dependent feedback (from various mortality agents) which are synchronized via a process of entrainment, or alignment of period and phase to the period and phase of an external rhythm. In the far north: spruce budworm reproductive success is clearly heat limited, and sensitive to a variety of temperature controls.

PART 2. YOU GOTTA KNOW THE BIOLOGY OF THIS CRITTER OF THIS CRITTER

Choristoneura Several Choristoneura actors: C. fumiferana C. biennis C. orae C. occidentalis

Spruce budworm is distributed across the continuous forest zone, but generally is not mapped all the way to northern tree limit. = 80% to 100% forested

August May/June The spruce budworm completes its life cycle within a 12- month period, but spread across 2 different years. First year events Second year eventsstart

SPRUCE BUDWORM LIFE CYCLE The spruce budworm completes its life cycle within a 12-month period, but spread across 2 different years. Larval Stage 1 L 1 The eggs hatch to produce the first instar (L 1 ) of the budworm. Larval Stage 2 L 1 L 2 The first instar (L 1 ) caterpillars develop into the second instar (L 2 ) caterpillars, which move by wind and find sites under bark scales. Here, they will spin silken cocoons for hibernation (overwintering). Larval Stage 3 L 2 L 3 In May, L 2 budworm, which are yellowish with dark brown heads, develop to the next instar (L 3 ), which either bore into needles or buds or spin silken webbing around new shoots and begin to feed on the needles within. Larval Stages 4, 5, 6 (L 6 ). The most damage to the foliage normally occurs early to mid-June when the larvae are in their final stage of development (L 6 ). Larger budworms with brown bodies (18-24 mm in length), black heads, and two rows of paired whitish spots down the back, can be spotted on shoots in June. Pupae L 6 After L 6, the budworms stop feeding and develop into brownish pupae, which in turn become moths. Moths (Adult) Moths mate and then the female lays eggs. Eggs Up to 300 green eggs per female are laid in masses of about eggs on the underside of the needles. Source:

Spruce budworm 2nd instar Spruce budworm egg mass sprucebud “worm” Spruce budworm 3rd instar sprucebud

Spruce budworm 4th instar

Photo: Robert A. Ott Larva stage 6 “… causes most damage to the foliage …” “… brown body, black head, two rows of paired whitish spots down the back, … on shoots in June.” spots down the back, … on shoots in June.”

Photo: Robert A. Ott Sprucebudwormpupa. male female Spruce budworm pupae

Spruce budworm adult moth

PART 3. SOME WAY THAT TEMPERATURE MIGHT MATTER. MIGHT MATTER.

“Overwintering mortality in the spruce budworm, Choristoneura fumiferana (Clem.), was measured between 1983 and 1990 in several natural stands of balsam fir, Abies balsamea (L.), in Quebec and Ontario. Overwintering losses (disappearance of larvae) averaged 25.2%, occurred mostly in late summer and early fall, …. overwintering We conclude that overwintering mortality does not result from adverse winter weather conditions or from gradual loss of hibernacula.” Regniere, J. and Duval. P Overwintering mortality of spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), populations under field conditions. Canadian Entomologist 130 (1):13-26.

“Temperature-dependent developmental rate of spruce budworm has been investigated extensively for almost all developmental stages… L1 developmental rate, however, has been overlooked. L1 L1 L1 Here, we divide L1 development into subphases based on morphological changes and behavioral events observed during the development of the stadium. We examine the effects of temperature on development time and survival rate for each development phase….L1 development time was significantly increased as rearing temperatures decreased…Although it took only a few more days for L1 to construct hibernacula at lower temperatures compared with insects reared at higher temperatures, it took a few additional weeks for the larvae to reach the 2nd stadium when they enter diapause. Therefore, temperature could have a significant impact on the timing of diapause initiation.” Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3):

Temperature control of spruce budworm 1st instar larva development rate (August). 13 o 23 o Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3): gs = green substance

Consolidation of green substance (gs) and formation of hibernaculum (hi) (August temperature control). Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3):

Excretion of green pellets in 1st instar. (August temperature control). “Han and Bauce (1993) reported that the excretion of green substance resulted in a lower super-cooling point as the insect prepared for overwintering. It is also possible that the green substance serves primarily as a camouflage for egg protection as spruce budworm eggs are laid on green needles and may be vulnerable to predation.” Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3):

Molt into 2nd instar larva. (August temperature control). Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3):

13 o C o C o C Han, E.; Bauce, E.; Trempe-Bertrand, F Development of the first-instar spruce budworm (Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3):

? “In Alaska, significant budworm damage was detected in 1978 on white spruce in many residential and park areas of Anchorage.” (Holsten: USDA Forest Service, Alaska Region Leaflet R10-TP-11) Analysis: G. Juday

~3.5 o C 100yr -1 Analysis: G. Juday

second instar to adult “A stochastic model of spruce budworm, Choristoneura fumiferana (Clemens), phenology on balsam fir, Abies balsamea (L.) Miller, and white spruce, Picea glauca (Moench) Voss, in northern Ontario was developed based on relationships between the proportion of budworms in each stage (second instar to adult) and accumulated degree- days (DD). Repeated calculations indicated that 8 degree C (46 F) was a suitable threshold for degree- day calculations. Tests of the model with independent data showed that it simulated spruce budworm development excellently. Model performance was superior compared with a previously published spruce budworm phenology model.” Lysyk, T.J Stochastic model of eastern spruce budworm (Lepidoptera: Tortricidae) phenology on white spruce and balsam fir. Journal of Economic Entomology 82 (4):

Growing Degree-day calculation DAY 1 Daily High 70 F Daily Low 50 F Mean daily 60 F Base temp. = 46 F GDD = 14 F DAY 2 Daily High 60 F Daily Low 40 F Mean daily 50 F Base temp. = 46 F GDD = 4 F 3-day accumulation = 18 GDD F DAY 3 Daily High 52 F Daily Low 40 F Mean daily 46 F Base temp. = 46 F GDD = 0 F

Accumulated degree days associated with peak stages of spruce budworm development 2nd instar 197 GGD(F) 3rd instar 217 GGD(F) 4th instar 280 GGD(F) 5th instar 366 GGD(F) 6th instar 492 GGD(F) 698 Pupa 698 GGD(F) 818 Adult 818 GGD(F) Base temperature = 46 F. Starting date (Lysyk) = 01 March Starting date (Juday -AK) = 01 April

Accumulated degree days associated with peak stages of spruce budworm development 2nd instar 109 GGD(C) 3rd instar 121 GGD(C) 4th instar 156 GGD(C) 5th instar 203 GGD(C) 6th instar 273 GGD(C) 388 Pupa 388 GGD(C) 454 Adult 454 GGD(C) Base temperature = 8 C. Starting date (Lysyk) = 01 March Starting date (Juday -AK) = 01 April

WE TEMPORARILIY INTERRUPT THIS PRESENTATION IN ORDER TO BRING YOU AN IMPORTANT MESSAGE ABOUT RECENT TEMPERATURE TRENDS IN BOREAL ALASKA

McGrath (foothils of Alaska Range) Bettles (foothills of Brooks Range) Analysis: G. Juday

Talkeetna Fairbanks Bettles

cold season growing season Last spring frost First fall frost Analysis: G. Juday

Factors Factors # days 70+F (21.1 C) # days 70+F (21.1 C) #days grow season #days grow season mean daily min. T mean daily min. T mean daily max. T mean daily max. T min. T of coldest 1 day min. T of coldest 1 day 2007 Analysis: G. Juday

WE NOW RESUME OUR REGULARLY SCHEDULED PRESENTATION

Budworm density data: R. Werner, J. Kruse nobudworms Datastart Budworm area data: AK For. Health Survey

July 7 ( July 6 Leap yr.) ?

Data: National Weather Service Analysis: G. Juday

1995 Acreage Data: Alaska Forest Health Survey Analysis: G. Juday

Budworm data: R. Werner, J. Kruse Analysis: G. Juday nobudworms Datastart

Budworm data: R. Werner, J. Kruse Analysis: G. Juday nobudworms Datastart 1-yr. lag

PART 4. OK, SO IT’S HERE, SO WHAT’S GOING TO HAPPEN?

(estimated) Data: G. Juday

NE British Columbia - Some useful recent articles: Alfaro, R.I., Taylor, S.P. R.G. Brown and J.S. Clowater Susceptibility of Northern British Columbia forests to spruce budworm defoliation. For. Ecol. and Management. 145: Burleigh, J.S., R.I. Alfaro, J.H. Borden, and S. Taylor Historical and spatial characteristics of spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) outbreaks in northeastern British Columbia. Forest Ecology and Management 168: Magnussen, Paul Boudewyn and René Alfaro Spatial prediction of the onset of spruce budworm defoliation. The Forestry Chronicle 80(4):

Source: Natural Resources Canada Cumulative Tree Mortality in white spruce (39 ecological impact plots in the Fort Nelson, B.C. Forest District) Mortality from high water table and windthrow Budworm No budworm

“Not known to breed in Alaska.” “Has occurred at Fairbanks, Haines, Pt. Barrow.” Armstrong Birds of Alaska. Cape May Warbler (Dendroica tigrina) : “ … the fortunes of its populations are largely tied to the availability of spruce budworms, its preferred food.” Dendron = tree Oikein = dwell

Tennessee Warbler (Vermivora peregrina): “A dainty warbler of the Canadian boreal forest, the Tennessee Warbler specializes in eating the spruce budworm. Consequently its population goes up and down with fluctuations in the populations of the budworm.” Probable rare breeder in Southeast Alaska, accidental in central Alaska. Armstrong Birds of Alaska. Vermis = worm

Bay-breasted Warbler (Dendroica castanea) : “A large warbler of the northern spruce forests, the Bay-breasted Warbler benefits from spruce budworm outbreaks when the caterpillars provide abundant food.” Accidental. Fairbanks. Armstrong Birds of Alaska. castanea = chestnut

Data: G. Juday

BARK spruce budworm damage heat/droughtlimitation Photo: C. Alix

1912 volcanic ash? 1993 & 95 spruce budworm defoliation 2004 record hot Data: G. Juday KILL ZONE

2007 spruce budworm defoliation Data: G. Juday 1968 (1967 flood)

recorded regular occurrence of summers warmer than Canadian Climate Center scenario

SUMMARY Spruce budworm is a major force shaping the North American boreal forest. Climate suitable for spruce budworm outbreaks have generally not been present in boreal Alaska until Seven stages of development (L1 - L6, Pupa) over 2 years. Winter cold temperatures do not appear to be a limitation. Egg hatch, L1, to L2 must get done in August, faster when warm. Greatest amount of damage from L6 feeding. L2 to adult must get done by mid-July (818 GDD F). Light attacks reduce w. spruce radial growth. Moderate attacks reduce growth and height growth points. Repeated severe attacks kill w. spruce. 3 boreal warblers have been missing from Alaska breeding birds.

PART 5. OK, SO WHAT HAPPENS NEXT?

Source: Natural Resources Canada NE British Columbia We concluded that timber losses are important in areas with maximum defoliation. Ecological impacts involved transformations of the forest that are likely transitory, considering the time scale of forestry (more than 100 years). Loss of biodiversity habitat is particularly important in areas that have been reserved for their old-growth characteristics. However, a changing climate may alter the long-term effects of budworm on the forest. The current outbreak has been longer and more severe than past outbreaks for which we have historical or tree-ring records. We cannot predict what these future changes will be, but the forest may change in different ways than it has in the past. The spruce budworm may also begin to attack forests where it has not been previously found.

PROBABLE SPRUCE BUDWORM FUTURE IN ALASKA BOREAL FOREST: Large outbreaks continue, intensify, and spread west, up, north W. spruce experiences high mortality and becomes less abundant Spruce budworm becomes limited by lack of contiguous susceptible stands of w. spruce W. spruce stabilizes population at lower level and in “refuge” stands in response to repeated outbreak cycles. Reduction/bottleneck for old-growth dependent species, esp. insectivorous migratory birds. 3 warbler species establish breeding populations in Alaska. W. spruce niche in uplands is partially displaced by: - black spruce - Alaska birch - aspen - lodgepole pine?

From scenario projection to forecasting?