Hardwood Diseases to Watch For

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Hardwood Diseases to Watch For

• Mark Gleason
• Iowa State University

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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Anthracnose

• Sycamore, maple, oak, walnut, ash, etc.
• Tiny lesions or blotches on leaves, scorched
  appearance
• Some tree species (e.g., sycamore) cankers on
  twigs, shoots, petioles and buds
• Defoliation weakens trees.

Ash
Maple
Walnut
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Anthracnose

• Weather conditions cool and moist
• Subsides with onset of warmer temperatures
• Fungi overwinter on infected debris, infected
  buds, cankered twigs.

Ash
Sycamore
Oak
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Anthracnose

• Management in forest stands impractical
• Thinning to increase air movement and sunshine
• Consider air movement when planting susceptible
  trees.

Oak
Ash
Sycamore
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Anthracnose

• Ornamental trees Rake fallen leaves.
• Fungicides
• Need at least 3 springtime sprays
• Seldom done
• Resistance
• London plane and red oaks more resistant than
  American sycamore and white oak

Dogwood
Sycamore
Maple
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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Rust

• Several different rusts Ash, cedar-hawthorn,
  etc.
• Need alternate host to complete life cycle
• Spartina for ash, cedar for hawthorn
• 5 spore stages

Ash rust
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Rust

• Yellow-orange leaf spots
• Galls, distorted tissues
• Repeated defoliation weakens trees

Cottonwood
Hawthorn
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Rust

• Ash
• Resistance
• Remove alternate host (Spartina marsh grasses)
• Cedar-hawthorn rust
• Resistant hawthorns and junipers
• If only a few junipers, physically remove galls
• Fungicides (sprayed on hawthorn not juniper)

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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Oak Wilt

• Very destructive in Eastern and Central U.S.
• Red oak group more susceptible than white oak
  group
• Trees in red oak group die 1-4 months after
  infection
• White oak group
• Bur oaks die in 1-7 yrs
• White oaks - up to 20 yrs

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Oak Wilt

• Red oak group -
• Symptoms appear in late spring or early summer
• Spore mats under bark
• Leaves discolor, wilt, fall off
• Streaks in outer sapwood
• White oak group -
• Symptoms more variable, slower to develop

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Oak Wilt

• Insect vectors picnic beetles (Nitidulids)
• Attracted to spore mats
• Fly to wounds on other oak trees, feed on sap
• Spread fungus up to several hundred feet

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Oak Wilt

• Avoid wounding April 1 through July 1
• Sap flows from wounds
• Paint wounds made from April 1 to first hard
  frost
• 80 of new outbreaks from wounding during
  construction
• Break root grafts
• Trenching machines or vibratory plows
• Woodlands Do nothing
• Often dies out naturally after local outbreaks

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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Verticillium Wilt

• Maple, ash, redbud, catalpa, etc.
• June and July
• Sudden wilting of leaves on one or several twigs
• Entire branch or crown eventually wilts.
• Decline or dieback of new twigs
• Yellowing foliage
• Sapwood discoloration

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Verticillium Wilt

• Fungus can survive in soil for many years.
• More common on stressed trees
• Management Remove infected trees.
• Replant with non-host trees
• Beech, birch, hawthorn, hickory, honey locust,
  ehite and bur oak, poplar, sycamore

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Diseases

• Foliar diseases
• Anthracnose diseases
• Rusts
• Wilts
• Oak wilt
• Verticillium wilt
• Cankers
• Butternut canker
• Strumella canker
• Hypoxylon root and basal canker

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Butternut Canker

• Butternut at risk due to this disease
• Pathogen may be imported
• Almost always fatal
• Appeared in southwestern Wisconsin in 1967
• Caused 80 decrease in butternuts in many states

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Butternut Canker
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Butternut Canker

• Infects trees through buds, leaf scars, insect
  wounds
• Cankers rapidly kill branches.
• Spores on braches spread by rainfall.
• Tree eventually dies.

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Butternut Canker

• Fungus survives 2 years on dead trees.
• Spread by rain, some beetles, birds
• No butternuts are resistant.
• Vigor of tree may be improved with proper pruning
  and tree care.

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Strumella Canker

• White oak
• Cankers diffuse, target-shaped
• Can girdle and kill saplings
• Target cankers formed by battle between fungus
  and tree
• Fungus produces dark brown pinhead-size
  structures on and near cankers.

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Strumella Canker

• Fungus enters through branch stubs.
• Tree may break at point of canker.
• Remove severely diseased trees in public areas.
• Forest stands No control
• Remove cankered trees during thinning.

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Hypoxylon Root and Basal Canker

• Caused by a fungus
• Birch, box elder, American elm, red and sugar
  maples, black, red, and white oaks, etc.
• Decayed wood often light in color with black
  stripes
• Spalted maple

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Hypoxylon Root and Basal Canker

• Invades wounds in bark
• Stroma on surface of exposed wood or dead bark
• Grayish white to brown, leathery
• Turns black and brittle with age
• Numerous small black fruiting structures are
  embedded in the stroma

Maple
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Hypoxylon Root and Basal Canker

• Airborne spores infect freshly wounded sapwood.
• May move from tree to tree via roots and hyphal
  growth through soil.
• Will eventually cause trees to lodge.
• No effective controls
• Remove infected trees to reduce spread.

Oak
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More information from ISU

• Verticillium wilt of woody plants SUL 16
• Oak wilt ID and management SUL 15
• Fungal cankers of trees SUL 11
• Diagnosing tree problems SUL 3
• Anthracnose of shade trees Pm 1280
• WEBSITE TO ORDER
• https//www.extension.iastate.edu/store/ListItems.
  aspx?CategoryID108

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Thank you!