dutch elm disease ophiostoma ulmi (syn. ceratocystis ulmi)
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Dutch Elm Disease• Ophiostoma ulmi
(syn. Ceratocystis ulmi)
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Dutch Elm Disease
• The American Elm is very susceptible
• Transmitted by elm bark beetles and root grafting
• Yellowing and wilting of branches in the crown of the tree
• Brown streaks in water conducting tissues
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Dutch Elm Disease Control• Sanitation of wood
– Remove dead or dying trees
• Bark beetles survive in wood piles– Burn or de-bark wood
• Manual trenching or Vapam
• Plant resistant elms– http://www.extension.umn.edu/projects/
yardandgarden/ygbriefs/p425dutchelm-resistant.html
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Fire blight• Erwinia amylovora
• Apple, pear, mountain ash, raspberry, contoneaster
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Fire blight control• Avoid highly susceptible cultivars and
rootstocks• Prune out blighted shoots (and sanitize
equipment) early – Scout after petal fall– Cut at least 8-12 inches below visible infection site
• Don’t fertilize to promote growth• Bacteriacides are available, generally not
effective– Can only prevent bloom infection (rare in MT)
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Brown felt blight• Herpotrichia juniperi and Neopeckia
coulteri
• Small trees buried under snow
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Brown felt blight control
• Usually none is warranted
• Causes some growth loss
• For ornamentals, foliage sprays of 5% Zineb or Maneb applied before first snowfall are effective in control.
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Cytospora canker of sprucea.k.a. Leucocytospora canker, Valsa canker
• Enters branches through wounds
• Spread by pruners, rain splash, animals
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Cytospora canker of spruce
• Prune affected branches back to the collar at the trunk
• Sanitize tools!– Rubbing alcohol or 10% bleach
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Rhizosphaera needle cast • Rhizosphaera kalhkoffii
• Rainsplash dispersed
• Symptoms:– Reduced needle retention– Dead (brown) older needles– Healthy, new needles do not show signs of
infection
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Rhizosphaera needle cast control
• Plant healthy trees• Good air flow in canopy• Don’t plant next to established (and/or
infected) trees• Bordeaux mixture or chlorothalonil (Daconil)• Spray in early June (new needles ½ length)
and again 3 wk later (new needles full length)
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Abiotic tree diseases• Drought: cottonwood and willows have
shallow root systems; will shed small branches and twigs
• Trees will shed leaves and needles to prevent water loss
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Drought recommendations• Slowly water affected trees regularly until mid-
August, then again following a killing frost• Do not water late into October; allow the tree
to complete the winter hardening process• Apply 5 to 10 gallons of water for each inch of
trunk diameter and the water should be applied within the radius of half the tree’s height.
• Do not fertilize