Cankers

Cankers
- General
  - localized area of dead bark tissue
  - causes
    - sunscald (=sunburn)
    - frost ("frost bite")
    - bacteria
    - fungus
  - infection court (= opening)
    - insect wound
    - mechanical wounds
    - lenticels (="stomata" on young bark)
    - leaf scars (on young twigs)
    - dead bark
  - host resistance - periderm (cork) & resin
    - exophylactic periderm
      - = external protection
      - original barks stretches (up to 100x's)
      - smooth bark (greenish)
      - peel (Arbutus) or continue to stretch (cherry & birch)
    - necrophylactic ("wound") periderm
      - = (dead) wound protection
      - = induced defense
      - break in periderm
        
        growth of stem
        
        wound
      - new cork cambium formed
      - ... soon afterward live tissue "outside" dies
  - types of cankers
    - annual (Phomopsis on Fd)
      - tree successfully contains fungus
    - perrenial / target (Nectria)
      - common worldwide - many spp.
      - fungus grows slowly in fall (tree dormant)
      - spring ... tree responds with callous tissue
      - repeat, and repeat, and repeat ...
    - diffuse (Chestnut Blight)
      - fungus quickly overpowers tree
- Atropellis piniphila DSA
  - Hosts & Range
    - Pl (Py)
    - south-central BC
  - Infection & Spread
    - ascospores can travel ~100m
    - infect apparently undamaged bark
    - likes it cool & moist
    - dense stands, high summer rainfall ... bad
  - Tree Resistance
    - trees <15 yr - immune
    - trees >15yr - resistance related to tissue age
      - 0-15 yr highly resistant
      - 15-25 yr - most susc. to new infection
      - 25+yr. v. few infections
    - vigourous trees can overgrow
  - Signs & Symptoms
  - Damage
    - value
      - stain, resin, deformity, weak wood ...
      - ... lumber losses up to ~33%
      - ... pulp chip rejects up to ~33%
      - overall value $$ loss of ~33%
    - reduced increment ~8% ... (50% Alb. study)
    - mortality
      - >1 canker to kill a tree
      - moist conditions: dense stands, high summer rainfall
  - Mgmt
    - @ harvest?
      - mix spp
      - cut residuals
    - @ JS?
      - if JS ... ~15 yr old (don't wait)
      - mix spp
      - FG criteria - NO stem cankers
- Other Examples
  - Phomopsis Canker DLP
    - Diaporthe (Phomopsis) lokoyae
    - Weak - usu. suppressed trees or drought
    - Fd (others) on coast
    - Elliptical, sunken cankers; black flecks
    - occasionally a problem in nurseries
  - Hypoxylon Canker DSH
    - Hypoxylon mammatum
    - ascomycetes
    - diffuse canker
    - Aspen, (poplars)
    - low incidence in BC, big elsewhere (~30% loss in Alb, Mich., Minn, Wisc.)
  - Chestnut Blight
    - the Pathogen
      - Cryphonectria parasitica
      - ascomycetes - native to China
      - video - "symptoms"
      - video - "comeback"
      - first documented in the Bronx Zoo 1904
      - by 1950 ... American Chestnut ... R.I.P.
    - the Tree
      - American Chestnut
      - range: e USA
      - large & fast growing
      - once accounted for 25% of trees in Appalachians ...
      - ... ~50% of forests in many regions
      - could regenerate by seed or root sprouts
      - great wood (crib .... coffin), decay resistant
      - edible nuts for wildlife, livestock & people
    - the Canker
      - diffuse: kills in 1-2 years
      - girdles tree quickly
      - roots & root collar are immune (get sprouts)
    - Hope?
      - tree breeding
        
        Chinese tree is resistant, but ...
        
        ... was bred as an orchard tree
        
        1st generation is 50:50
        
        ... back breed until only 1/16th Chinese (1st 1/2 of video)
      - Transgenics (same video)
        
        pathogen produces oxalic acid (="active ingredient")
        
        hypovirulent fungi produce less
        
        gene from wheat spliced into tree genes ...
        
        ... can now produce oxalate oxidase (enzyme) ...
        
        ... = defense mechanism
      - hypovirulence (poor sound)
        
        fungus is infected (mutated by) a virus
        
        result: low virulence of the fungus ...
        
        ... fungus is less lethal
        
        crossing "normal" fungus with hypovirulent strain yields the hypovirulent strain
        
        best in urban/orchard situation as direct control
        
        transmission to pop'n in Europe but not US (& Michigan)
      - soil compress
        
        only exposed roots get cankers ...
        
        on small cankers on young trees