White fir Recovery and Mortality following the Douglas-fir Tussock Moth Bear Mountain Outbreak...

White firWhite fir Recovery and Mortality Recovery and Mortality

following thefollowing theDouglas-fir Tussock MothDouglas-fir Tussock Moth Bear Mountain Outbreak Bear Mountain Outbreak

(2005-2007)(2005-2007)Siskiyou County, CASiskiyou County, CA

2 - 4 years post outbreak2 - 4 years post outbreak

Donald R. Owen

Background information on DFTM, Orgyia psuedotsugata

•White fir is the principal host in CA and SW USDouglas-fir and grand fir are principal hosts elsewhere

•One year life cycle with egg hatch in June and pupation in July•5-6 instars typical•1st 3 instars account for 10% of defoliation•Last instar accounts for > 60% of the defoliation•Outbreaks are cyclic with a 7-10 year return interval

Outbreaks may last 1-4 years•In order to cause significant damage, an outbreak would typically go through 3 phases, each phase corresponding to one DFTM generation (one year)

• Release – rapid population increase; little, if any, noticeable defoliation

• Peak – highest population and most severe defoliation; natural enemies begin to exert control by the end of the generation

• Decline / Collapse – population initially high, but natural enemies cause population collapse; defoliation may be more widespread, but less severe

Damage

•Damage = top kill, mortality, and growth loss•Defoliation is measured as the % of crown completely defoliated•90% of mortality occurs in trees with > 90% defoliation•Trees with < 50% defoliation rarely die•Top-kill follows a similar trend•Defoliation varies significantly across the landscape, with heavy defoliation occurring in hotspots up to 50 acres in size•Hotspots typically occur on ridges, upper slopes, and poorer sites•To prevent damage, control should target the Peak Phase and concentrate on predicted hot spots•Control during the Decline Phase may reduce defoliation that year, but may have negligible effect on top kill and mortality•Overall, stands experience growth loss initially, but long-term effect is usually neutral or positive

Bear Mountain DFTM Outbreak

2005 No early detection monitoring in this area; population release occurs without notice

2006 Peak phase; high egg mass counts in some locations in the fall, but parasites and dead DFTM larvae and pupae are common; egg masses are relatively small and there is a low ratio of egg masses to pupal cases; 2,455 acres of defoliation

2007In hotspots, some trees or tops of trees do not break bud (mortality and top kill); DFTM population is initially high, but shows noticeable decline by 3rd instar in areas with the heaviest defoliation; parasites abundant; no egg masses could be found in the fall (population collapse); 7,444 acres of defoliation. This outbreak followed the typical 3-yr sequence of population release, peak, and decline

Defoliation

as mapped from aerial survey

in 2006

Peak Phase of the

Bear Mountain Outbreak

Outbreak centered on Bear Mountain and north of Sheepheaven Butte

Expansion of the outbreak in 2007

was due to mostly light defoliation in surrounding areas

WF WF RecoveryRecovery – Bear Mtn DFTM – Bear Mtn DFTM OutbreakOutbreak

2007

2009

Light defoliation

Photo pt 10

2011

WF WF Recovery Recovery – Bear Mtn DFTM – Bear Mtn DFTM OutbreakOutbreak

2009

2007

Photo pt 13

5-20 % defoliation 201

1


2007

2009

Photo pt 13

5-20 % defoliation

2011

2007


200720 % defoliation

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2009

2011


2007

2009

20 % defoliation

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2007

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25-55 % defoliation

2011


2007

2009

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25 % defoliation

2011


2007

2009

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55 % defoliation

2011


2007

2009

25 - 30 % defoliation

Photo pt 05

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2009


Photo pt 05

2007201

12007


2009

33 % defoliation

Photo pt 07

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2011


2007

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33 % defoliation

Photo pt 07

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2007

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40 % defoliation

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2007

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Photo pt 14

50 % defoliation 201

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2009

2007

Photo pt 14

50 % defoliation

2011


2007

2009

Photo pt 17

55 % defoliation2011


2007

2009

Photo pt 17

55 % defoliation

2011


2009

200760 % defoliation

Photo pt 03

2011


2007

200960 %

defoliation

Photo pt 03

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2007

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Photo pt 06

2011



2007 200

9

Photo pt 06

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2007

2009

60 % defoliation

Photo pt 11

2011


2007

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Photo pt 19

60 % defoliation

2011

WF WF MortalityMortality – Bear Mtn DFTM – Bear Mtn DFTM OutbreakOutbreak

2007

2009 (dead 2008)85 %

defoliation

Photo pt 04

WF WF Mortality Mortality – Bear Mountain DFTM – Bear Mountain DFTM OutbreakOutbreak

2007

2009 (dead 2008)

90 % defoliation

Photo pt 01

WF WF MortalityMortality– Bear Mtn DFTM – Bear Mtn DFTM OutbreakOutbreak

2007

2009(dead 2008)

Photo pt 16

95 % defoliation


2009 (dead 2008)

2007

Photo pt 18

95 % defoliation

2011


2007

2009 (white fir dead

2008)

WF 90-100 % defoliation

Ponderosa pine

Photo pt 08

2007

2009

Photo pt 08

2011

Ponderosa Pine Ponderosa Pine RecoveryRecovery – Bear Mtn – Bear Mtn DFTM OutbreakDFTM Outbreak

Douglas-fir Douglas-fir RecoveryRecovery – Bear Mtn – Bear Mtn DFTM OutbreakDFTM Outbreak

2007

2009

Photo pt 15

1-30 % defoliation

2011

DF DF RecoveryRecovery – Bear Mtn DFTM – Bear Mtn DFTM OutbreakOutbreak

2007 200

9

Douglas-fir

Photo pt 15

1-30 % defoliation

2011

2007

References Beckwith, RC. 1978. In: The Douglas-fir Tussock Moth: A Synthesis. MH Brookes, RW Stark, and RW Campbell, eds. USDA For. Serv. Tech. Bull. No. 1585. p 66. Mason, RR and RF Luck. 1978. In: The Douglas-fir Tussock Moth: A Synthesis. MH Brookes, RW Stark, and RW Campbell, eds. USDA For. Serv. Tech. Bull. No. 1585. p 40 & 44. Mason, RR and JW Baxter. 1970. Food preference in a natural population of the Douglas-fir tussock moth. J. Econ. Entomol. 63(4):1257-9. Shepard, RF, DD Bennett, JW Dale, S Tunnock, RE Dolph, and RW Their. 1988. Evidence of synchronized cycles in outbreak patterns of Douglas-fir tussock moth, Orgyia psuedotsugata (McDunnough)(Lepidoptera:Lymantriidae). Mem. Ent. Soc. Can. 146:107-21 Torgersen, TR and DL Dahlsten. 1978. In: The Douglas-fir Tussock Moth: A Synthesis. MH Brookes, RW Stark, and RW Campbell, eds. USDA For. Serv. Tech. Bull. No. 1585. p 47-53. Wickman, BE. 1963. Mortality and growth reduction of white fir following defoliation by the Douglas-fir tussock moth. USDA For. Serv. Res. Pap. PSW-7. 14p. Wickman, BE. 1978. A case study of a Douglas-fir tussock moth outbreak and stand conditions 10 years later. USDA For. Serv. Res. Pap. PNW-244. 22p.

References continued

Wickman, BE. 1979. Douglas-fir tussock moth handbook. How to estimate defoliation and predict tree damage. Ag. Hdbk No. 550. 15p. Wickman, BE. 1980. Increased growth of white fir after a Douglas-fir tussock moth outbreak. J. For. 78:31-33. Wickman, BE. 1986. Growth of white fir after Douglas-fir tussock moth outbreaks: long-term records in the Sierra Nevada. USDA For. Sev. Res. Note PNW-440. 8p. Wickman, BE. 1988. Tree growth in thinned and unthinned white fir stands 20 years after a Douglas-fir tussock moth outbreak. USDA For. Sev. Res. Note PNW-RN-477. 11p. Wickman, BE.1990. Mammoth Lakes revisited – 50 years after a Douglas-fir tussock moth outbreak. USDA For. Sev. Res. Note PNW-RN-498. 6p. Wickman, BE, RR Mason, and CG Thompson. 1973. Major outbreaks of Douglas-fir tussock moth in Oregon and California. USDA For. Serv. Gen. Tech. Rep. PNW-5. 18p.

Williams, CB Jr, JM Wenz, DL Dahlsten, and NX Norick. 1979. Relation of forest site and stand characteristics to Douglas-fir tussock moth (Lep. Lymantriidae) outbreaks in California. Bull. Soc. Entom. Suisse. 52:297-307.

White fir Recovery and Mortality following the Douglas-fir Tussock Moth Bear Mountain Outbreak...

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