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 Alan, 
  
I have experienced later season fire blight on 
Cortland apples as well as Gala and Jonafree on Mark rootstock due to severe 
thunderstorm activity creating a "trauma" which can  
spread "canker blight", another form of fire 
blight that results in "shoot blight".  I think i may have posted the 
different forms of  
fire blight once before last winter.  Here 
is part of that post that may help. 
  
  
  
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       In years when blossom 
      infections do not occur, the primary sources of inoculum for the shoot 
      blight phase are the overwintering cankers and, in particular, young water 
      sprouts near these cankers, which become infected as the bacteria move 
      into them systemically from the canker margins.  
      
       
        
        
          | Such systemic shoot infections, called "canker blight", 
            are apparently initiated about 200 DD greater than 55 F (111 DD 
            greater than 13 C) after green tip, although visible symptoms may 
            not be apparent until the accumulation of at least 300 DD greater 
            than 55 F (167 DD greater than 13 C) after green tip. In the absence 
            of blossom infections, the development of shoot blight infections is 
            often localized around areas with overwintering cankers.  
             
             Although mature shoot and limb tissues 
            are generally resistant to infection by E. amylovora, injuries 
            caused by hail, late frosts of 28 F (-2 C) or lower, and high winds 
            that damage the foliage can create a trauma blight situation in 
            which the normal defense mechanisms in mature tissues are breached 
            and infections occur. Instances of trauma blight are known to occur 
            even on normally resistant cultivars like 'Delicious'. 
            Rootstock blight, yet another phase of 
            fire blight, is associated primarily with the highly 
            susceptible M.26, M.9 and Mark rootstocks in apple trees. On these 
            trees, just a few blossom or shoot infections on the scion cultivar 
            can supply bacteria that then move systemically into the rootstock 
            where a canker often, but not always, develops and eventually 
            girdles the tree. Trees affected by rootstock blight generally show 
            symptoms of decline and early death by mid to late season, but may 
            not be apparent until the following 
      spring.  |    |  
  
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       If you would like any further information 
      on late season fire blight, send me an e-mail and I can forward you the 
      information I have on file.  Hopw this helps! 
         | 
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  ----- Original Message -----  
  
  
  Sent: Sunday, November 25, 2007 7:22 
  AM 
  Subject: [NAFEX] Late fireblight 
  
  
  I have been growing my own and managing for others a wide range of 
  varieties of pears here in the vicinity of southeastern NY for almost 
  20 years.  Based on what I gathered from the literature, I began 
  with the anticipation of ongoing warfare with fire 
  blight.  Experience has not met anticipation and fire blight 
  has not been a major issue.  On most sites, including my own 
  orchard, I've never seen a single strike.  Knock on wood.  
    
  There are two sites, however, where this tree-killer has reared its ugly 
  head but the timing of its attacks are strictly Che Guevara-  small 
  attacks when least expected.  I've always read that fire blight occurs in 
  the spring starting in the open blossoms with pollinaters as 
  vector.  In the two orchards where it has appeared the symptoms did not 
  become visible until mid-July.  In one site it hit a Bosc pear for 2 
  straight seasons while leaving an adjacent Bosc and a Seckel alone.  So 
  far, Ive had to remove about 50% of the tree.  
    
  In the other site the strikes come about the same time and have also 
  appeared for the 2nd season but have been more widespread 2nd time 
  around.  The first season only the Bosc was badly damaged but this year 
  the quinces, a red Bartlett and a Seckel also had some damage.  There was 
  also a scattering of strikes throughout the various varieties of apples but 
  for these trees the damage was minor.  
    
  I'm guessing the vector to be leaf-hoppers but that's an uneducated 
  leap.  Does anyone out there have some information about late season fire 
  blight?  
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