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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous > Cotoneaster > Spots or blotches on leaves

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Cotoneaster > Leaves > Spots or blotches on leaves

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  • Image: Codling moth 1
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Powdery Mildew
Podosphaera clandestina

  • Patches of white, powdery or felt-like fungal patches on leaf surfaces
  • Leaves and shoots may be puckered or distorted
  • New leaves and shoots may be smaller than normal
  • Powdery white fungal growth may be present on ripened berries
  • Symptoms may develop over a single season, or over several years
  • More information on powdery mildew
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Pear Sawfly (Pear Slug)
Caliroa cerasi

  • Larvae feed on upper surface of leaf between the veins, "windowpaning" the leaf as they feed
  • Damaged leaves often have a grayish appearance before turning brown
  • Larvae normally feed about 4 weeks beginning in June; a second generation may start in August
  • Larvae are one half inch long, shiny and slug-like and are normally dark olive green in color
  • More information on Pear Sawfly
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  • Image: Fire Blight 1
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Quince Rust
Gymnosporangium clavipes

  • Fruit becomes covered with orange tube-like spore producing structures
  • Powdery orange colored spores are released in midsummer to fall
  • Spindle-shaped swellings occur on petioles and green twigs
  • Cankers may form on stems and cause dieback
  • Occasionally yellow to orange leaf spots form
  • More information on Quince Rust
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  • Image: Fire Blight 1
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Hawthorn Lacebug
Corythuca cydoniae

  • Feed on underside of leaves causes yellowish pin-prick stippling on upper surface
  • Small drops of varnish-like excrement is found on underside of leaves
  • Heavy feeding may cause damaged areas to coalesce forming blotches
  • Active throughout the growing season, although damage is most noticeable during late summer
  • Adults are .125 to .25 inches long, have light colored bodies with black bands with ornately sculptured wings that are flat and lacey from above.
  • More information on Hawthorn Lacebug
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  • Image: Fire Blight 1
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Sooty Mold

  • Black, brown or gray soot-like covering on leaf surfaces, twigs or branches
  • Sticky, shiny secretions on leaves from sap-sucking insects (e.g., wooly apple aphid)
  • Insects or signs of insect damage (distorted, pin-prick feeding marks, etc.) may be seen on leaves or twigs above the most heavily affected moldy areas.
  • More information on Sooty Mold

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