2. Douglas-fir Tussock Moth - DFTM Orgyia pseudotsugata

3. DFTM Larva

4. DFTM LIFE CYCLE

5. First instar larvae “Spinning down” which will “balloon” to new location

6. Douglas-fir Tussock Moth Larvae

7. “Red” trees caused by young larvae

8. Dead trees from older larvae.

9. Douglas-fir Tussock Moth - Male

10. Douglas-fir Tussock Moth – Female Resting upon pupal case – note hairs

11. Egg cases

12. DFTM CAUSED MORTALITY

13. Natural Control Factors Normally populations keep low during with over 90% of larvae and 75% of pupae are killed by natural factors. Viruses - Two naturally occurring types Nuclear polyhedrosis virus (NPV) and granulosis virus (GV)

14. NPV killed Douglas-fir tussock moth larva

15. NPV Particles – greatly enlarged

16. Natural Control Factors Parasites: Many Dipterous parasitoid ovipositing on DFTM eggs

17. Natural Control Factors Predators: Birds, especially Chickadees, small mammals and ants Starvation – simply run out of leaves to feed on High summer temperatures kill larvae Withstand cold winter temperatures but not high

18. Outbreaks occur at about 9 year intervals & last 4 years In the past, outbreaks often detected in year 3, treated in year 4 Pest Management – When & Why

19. Interactions - DFTM and Bark beetles

20. Pheromone traps – sticky glue & pheromone

21. When insects in traps begin to increase – then treat stand

22. Management Considerations Chemical Control Biological Control DFTM Pheromones (Z) – 6-heneicosen-11-one Nuclear polyhedrosis virus (NPV) Bacillus thuringiensis (Bt) Will give good control if applied when the new foliage first appears.

23. Helicopter application of NPV

25. NPV Study - Control Plot (Not sprayed)

26. NPV Study - Treated with virus plot

27. Ecology Stand Management

28. In 1974 The EPA granted emergency authorization to the US Forest Service to use DDT for control of the Douglas-fir Tussock Moth Several hundred thousand acres were sprayed and the moth population crashed in the treated areas. Forest Service Researchers also established a “control” area of about the same size where no treatment was made. The Moth population crashed in those areas too. This was the last legal use of DDT in the U.S. Science vs Politics (Cost vs Benefit)

29. End of Douglas Fir Tussock Moth Section