1. White fir Recovery and Mortality following the Douglas-fir Tussock Moth Bear Mountain Outbreak (2005-2007) Siskiyou County, CA 2 - 4 years post outbreak White fir Recovery and Mortality following the Douglas-fir Tussock Moth Bear Mountain Outbreak (2005-2007) Siskiyou County, CA 2 - 4 years post outbreak Donald R. Owen

2. Background information on DFTM, Orgyia psuedotsugata White fir is the principal host in CA and SW US Douglas-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 1 st 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

3. 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

4. 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 2007 In 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 3 rd 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

5. 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

6. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Light defoliation Photo pt 10 2011

7. WF Recovery – Bear Mtn DFTM Outbreak 20092007 Photo pt 13 5-20 % defoliation 2011

8. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 13 5-20 % defoliation 2011 2007

9. WF Recovery – Bear Mtn DFTM Outbreak 2007 20 % defoliation Photo pt 12 2009 2011

10. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 20 % defoliation Photo pt 12 2011

11. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 20 25-55 % defoliation 2011

12. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 20 25 % defoliation 2011

13. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 20 55 % defoliation 2011

14. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 25 - 30 % defoliation Photo pt 05 2011

15. WF Recovery – Bear Mtn DFTM Outbreak 2009 25 - 30 % defoliation Photo pt 05 2007 2011 2007

16. WF Recovery – Bear Mtn DFTM Outbreak 2009 33 % defoliation Photo pt 07 2007 2011

17. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 33 % defoliation Photo pt 07 2011

18. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 40 % defoliation Photo pt 02 2011

19. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 40 % defoliation Photo pt 02 2011

20. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 14 50 % defoliation 2011

21. WF Recovery – Bear Mtn DFTM Outbreak 2009 2007 Photo pt 14 50 % defoliation 2011

22. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 17 55 % defoliation 2011

23. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 17 55 % defoliation 2011

24. WF Recovery – Bear Mtn DFTM Outbreak 2009 2007 60 % defoliation Photo pt 03 2011

25. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 60 % defoliation Photo pt 03 2011

26. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 70 - 30 % defoliation Photo pt 06 2011

27. WF Recovery – Bear Mtn DFTM Outbreak 70 - 30 % defoliation 2007 2009 Photo pt 06 2011

28. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 60 % defoliation Photo pt 11 2011

29. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 60 % defoliation Photo pt 11 2011

30. WF Recovery – Bear Mtn DFTM Outbreak 20072009 Photo pt 19 60 % defoliation 2011

31. WF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 19 60 % defoliation 2011

32. WF Mortality – Bear Mtn DFTM Outbreak 2007 2009 (dead 2008) 85 % defoliation Photo pt 04

33. WF Mortality – Bear Mountain DFTM Outbreak 2007 2009 (dead 2008) 90 % defoliation Photo pt 01

34. WF Mortality– Bear Mtn DFTM Outbreak 2007 2009 (dead 2008) Photo pt 16 95 % defoliation

35. WF Mortality– Bear Mtn DFTM Outbreak 2009 (dead 2008) 2007 Photo pt 18 95 % defoliation

36. 2011 WF Mortality– Bear Mtn DFTM Outbreak 2007 2009 (white fir dead 2008) WF 90-100 % defoliation Ponderosa pine Photo pt 08

37. 20072009 Photo pt 08 2011 Ponderosa Pine Recovery – Bear Mtn DFTM Outbreak

38. Douglas-fir Recovery – Bear Mtn DFTM Outbreak 2007 2009 Photo pt 15 1-30 % defoliation 2011

39. DF Recovery – Bear Mtn DFTM Outbreak 2007 2009 Douglas-fir Photo pt 15 1-30 % defoliation 2011 2007

40. 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.

41. 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.