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Douglas-fir Tussock Moth - DFTM Orgyia pseudotsugata

Douglas-fir Tussock Moth - DFTM Orgyia pseudotsugata. DFTM Larva. DFTM LIFE CYCLE. First instar larvae “Spinning down” which will “balloon” to new location. Douglas-fir Tussock Moth Larvae. “Red” trees caused by young larvae. Dead trees from older larvae.

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Douglas-fir Tussock Moth - DFTM Orgyia pseudotsugata

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  1. Douglas-fir Tussock Moth - DFTM Orgyia pseudotsugata

  2. DFTM Larva

  3. DFTM LIFE CYCLE

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

  5. Douglas-fir Tussock Moth Larvae

  6. “Red” trees caused by young larvae

  7. Dead trees from older larvae.

  8. Douglas-fir Tussock Moth - Male

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

  10. Egg cases

  11. DFTM CAUSED MORTALITY

  12. 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)

  13. NPV killed Douglas-fir tussock moth larva

  14. NPV Particles – greatly enlarged

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

  16. 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

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

  18. Interactions - DFTM and Bark beetles

  19. Pheromone traps – sticky glue & pheromone

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

  21. 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.

  22. Helicopter application of NPV

  23. NPV Study - Control Plot (Not sprayed)

  24. NPV Study - Treated with virus plot

  25. Ecology Stand Management

  26. Science vs Politics (Cost vs Benefit) • 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.

  27. End of Douglas Fir Tussock Moth Section

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