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Hemlock woolly adelgid resistance E. Preisser, B. Maynard, R. Casagrande

Hemlock woolly adelgid resistance E. Preisser, B. Maynard, R. Casagrande. No reported resistance in Tsuga canadensis or T. caroliniana. Western hemlock. W. hemlocks resist eastern HWA and E. hemlocks resist western HWA. Mountain hemlock. Difficult to grow in northeast.

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Hemlock woolly adelgid resistance E. Preisser, B. Maynard, R. Casagrande

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  1. Hemlock woolly adelgid resistanceE. Preisser, B. Maynard, R. Casagrande No reported resistance in Tsuga canadensis or T. caroliniana

  2. Western hemlock W. hemlocks resist eastern HWA and E. hemlocks resist western HWA

  3. Mountain hemlock Difficult to grow in northeast

  4. Chinese and Japanese hemlocks are HWA-resistant (But poor choice for landscape or forest)

  5. Todd Caswell Richard Casagrande Laura Ingwell Brian Maynard Evan Preisser Laura Radville Are some eastern hemlocks resistant to HWA?

  6. Preisser et al. (2008) sampled 142 hemlock stands in 2005

  7. In FOREST stands with ≥95% mortality Mature (>10 m) trees Appeared relatively healthy largely free of HWA and elongate hemlock scale INNATE OR ENVIRONMENTAL? “Potentially resistant hemlock”

  8. Propagate cuttings Grow under identical conditions Infest with HWA under controlled conditions Evaluating hemlock resistance

  9. CT sample sites

  10. Burnham Brook, CT

  11. Lyme, CT

  12. Madison, CT

  13. Rooting hemlocks Two variables: time of season and hormone treatments

  14. Propagation bed

  15. January 2006 cuttings

  16. Spring 2006root ratings 0-3

  17. Results of 2006 winter cuttings (number rooted/number treated)

  18. 2007 rooting results Treatment 0 = ControlTreatment 1 = 1:1 ratio of Dip ‘n Grow to water Treatment 2 = 1:2 ratio of Dip ‘n Grow to water

  19. Rooted cutting in June

  20. HWA inoculation

  21. Inoculated plant

  22. 2006 HWA results 3

  23. Mark Mayer’s NJ “bulletproof stand” Courtesy of Mark Mayer

  24. 2007 sample sites100 cuttings each from • 6 CT Trees • 5 NJ Trees (Mark Mayer) • 2 PA Trees (Scott Stitzer) • 1 MD Tree (Dave Mausel) • 4 Control Sites (MA, NY) 18 Trees (1800 cuttings)

  25. 2007 rooted cuttingsheld for testing in spring 2009 • Allow additional time to recover from rooting and outgrow field environmental effects • Provide 12 months of growth under standardized conditions • Improve timing of plant growth and HWA inoculation

  26. HWA inoculation tests – 2009 • Inoculate all rooted cuttings with HWA in early spring • 3 groups: control, resistant, and cuttings from western hemlocks • Assessed HWA settlement and survival

  27. 2009 HWA inoculation results

  28. 2010 HWA inoculation results 6 4 HWA crawlers/cm) 2 0 Resistant Control

  29. Progress towards providing nurseries with plants • Planning third large-scale test of HWA resistance in spring 2011 • Carried out large-scale grafting experiment in 2010 – results in summer 2011 • Set up ‘hemlock hedge’ of resistant trees for cuttings and assessment of growth form and HWA resistance

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