Wilts

Wilts
- general overview
  - "hardwood disease" (but DRB?)
  - ascomycetes
  - insect vector (bark beetles) & and/or root contact
  - fungus invades the xylem (sapwood)
  - cause of death
    - blockage of water conducting vessels
      - by tree's own defence mechanisms ...
        
        ... gums and ...
        
        ... tyloses (cell tissue that plugs the vessels in the xylem)
      - by the fungus itself
    - toxins produced by fungus
- Dutch Elm Disease ("DED")
  - Overview
    - Ophiostoma ulmi (Ceratocystis) & O. novo-ulmi (more virulent)
    - named as it was first noted and described in Holland
    - originated in the orient
    - introduced to NA via green lumber with bark (USA '30,Quebec '45)
    - vectored by bark beetles (European & American)
      - American - feeds on larger branches and moves to lower stem to OW
      - European - feeds on small twigs in crown
    - legislation - e.g. Sask.
  - host & range
    - Elms ... obviously
    - worldwide ditribution
      - w. Asia, Europe, Canada (not Alta or BC), USA & N.Z.
      - BC & Alta - one of the few areas in the world free of DED
      - Alta has the largest pop'n of DED-free American elms in the world ...
      - over 200,000 elms valued at over $600 million
  - signs & symptoms
  - Mgmt
    - early attempts - kill beetle with DDT
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      - video
    - Elms maintained in some areas only by agressive ($$) action
      - monitoring
      - pruning
        
        branches if <5% crown & within 2-3 weeks
      - sanitation
        
        cutting tree? careful if adj. tree healthy but grafted
      - root grafts
        
        reactive or preventative
      - spraying for beetle
        
        likely best for American beetle
      - firewood
      - inject preventative fungicide
        
        lasts 1-3 years
      - inject vaccine - Dutch Trig
      - breeding for resistance
      - trap trees
        
        infected trees injected with silvicide
        
        bark dries fast and beetle cannot complete life cycle
        
        and other beetles are attracted to the tree (="sink")