Canker Diseases

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Canker Diseases

• ESC 432 Forest Pathology
• Reading Text Chapter 14, pages 341-347

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Cankers

• Fungi grow in cambium
• Kill by girdling
• Variable in disease severity
• Mostly Ascomycetes and Deuteromycetes
• Most common on hardwood hosts

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Stem Anatomy
Phloem
Xylem
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Mode of Action

• Canker fungi feed on nutrients and carbon in
  vascular system
• Toxins that kill host tissue
• Enzymes to decompose wood
• Host responds with callusing

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Disease Cycle

• Spores infect through wounds or branch stubs in
  wet weather
• The fungus invades the host
• Sporulation in killed bark, usually asexual
• Mycelium over-seasons as a saprobe in dead bark
  or soil and re-infects when host defenses are low

Wound which became infected from splashing of
infested soil
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Types of Cankers

• Opportunists (saprobes contributing to declines)
• Annual cankers
• Target cankers caused by facultative parasites
• Diffuse cankers

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Opportunists
Fusicoccum

• Associated with weakened trees or branches
• More aggressive when trees are drought or shade
  stressed
• Often part of a disease complex

Hypoxylon
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Annual Cankers

• Fungus is only active for one season
• Canker is inactivated by host response
• Stressed or injured trees can get multiple
  cankers
• No impact on tree growth, but lumber is degraded

Fusarium solani on yellow poplar
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Perennial Target Cankers

• Balanced interaction of fungus and host
• Fungus destroys a small amount of cambium each
  year
• Host walls off fungus
• Fungus grows when host is dormant

Nectria target canker
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Diffuse Cankers

• Usually very aggressive pathogens
• Host unable to produce a callus wall
• Expands during the growing season

Cryphonectria parasitica, chestnut blight
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Some examples

• Madrone decline
• Pitch canker
• Sudden oak death

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Pacific Madrone Decline

• Host Pacific madrone (Arbutus menziesii)
• Pathogens
• Fusicoccum arbuti (Anamorph asexual)
• Botryosphaeria spp. (Teleomorph sexual
• not found yet)

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Fusicoccum arbuti formerly Nattrassia mangiferae

• Perennial canker on stems and branches
• Opportunistic, worse when host is under water
  stress
• Can be aggressive on some individuals

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Also gets on small branches, leaves

• Ubiquitous
• Opportunistic
• Normally kills shaded, suppressed branches
• On madrone (Northern range), kills branches
  water-stressed by Nattrassia cankers

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Madrone Decline

• More declining trees noticed after periods of
  drought
• Older trees more susceptible
• Important factors
• Fire suppression
• Climate change
• Introduced pathogen?

Declining madrone trees at Seward Park, Seattle,
WA
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Pitch Canker

• Host Monterey pine (Pinus radiata)
• Pathogen Fusarium circinatum
• Significant damage on native Monterey pines in CA
• Insects important in disease cycle

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Distribution
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Disease cycle and insect vectors

• Twig beetles
• Engraver beetles
• Cone beetles

All are in the family Scolytidae
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Management

• Plant resistant species or genotypes
• Induced resistance and remission
• Chemical control for nursery trees
• Remove dead material
• Promote natural regeneration

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Sudden Oak Death

• Hosts gt40 species including
• Susceptible Tanoak, Coast live oak, Black oak
• Foliar Buckeye, California bay laurel, Pacific
  madrone, Rhododendron, Evergreen huckleberry,
  Bigleaf maple
• Pathogen Phytophthora ramorum (Oomycetes)
• Occurs in central coast of CA, southern OR, Europe

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Phytophthora ramorum

• Closest relative P. lateralis
• Cool, moist climates
• Airborne
• Two mating types
• A1 European
• A2 North American

Hyphae in tanoak lenticel
Zoosporangia
Chlamydospore On bay leaf surface
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Distribution

• European A1
• Belgium
• Scandinavia
• France
• Germany
• Ireland
• UK
• Spain
• Canada (B. C.)
• Oregon (Clackamas Co.)

• North American A2
• Central coastal California
• Curry County, OR
• King County, WA
• Belgium

Forests Nurseries, horticultural plants
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Symptoms

• Bleeding cankers (oaks and tanoaks)
• Dieback and leaf spots (foliar hosts)
• Wilting (tanoak)
• Hypoxylon fruiting on dead or dying trees

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Rhododendron Symptoms
Leaf necrosis
Shoot blight and dieback
Staining under bark
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Douglas-fir and Redwood
On succulent shoots and foliage, not woody
material
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How it spreads

• P. ramorum isolated from plant debris, soil,
  nursery plants, rain-splash
• Human movement of infested materials
• Birds
• Soil/rain for local or tree-to-tree spread
• Foliar hosts
• Insect vectors being investigated

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Management

• Quarantine plant materials and soil
• Wash vehicles and shoes after visiting SOD areas
• Composting kills P. ramorum
• Phosphorous acid injections on valuable trees