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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Roses > Spots on stems

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Roses > Stem > Spots on stems

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  • Image: Canker 1
  • Image: Canker 2
  • Image: Canker 3

Canker
Several different fungi

  • Dead branch within otherwise healthy plant
  • Light colored blotches or patches, often with a reddish purple border, along dead stem
  • Some patches may have flaky, loose or cracked epidermis (surface layer)
  • Tiny black bumps may be seen on dead area of stem
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  • Image: Powdery Mildew 1
  • Image: Powdery Mildew 2
  • Image: Powdery Mildew 3

Powdery Mildew
Sphaerotheca pannosa

  • Powdery white coating on leaves, stems, flower buds and flower stalks
  • Leaf tissue may be tinted red around the infection
  • Leaves can be twisted or curved at the site of infection
  • Infection often most severe on young leaves
  • Typically occurs mid to late summer
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  • Image: Gray Mold 1
  • Image: Gray Mold 2
  • Image: Gray Mold 3

Gray Mold
Botrytis cinerea

  • Small red rings or flecks on white or light colored petals
  • Brown irregular spots on petals
  • Completely brown, curled over, dead flower buds
  • Brown sunken area on stem
  • Gray fuzzy spores produced in cool wet weather
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  • Image: Black Spot 1
  • Image: Black Spot 2
  • Image: Black Spot 3

Black Spot
Diplocarpon roseae

  • Purplish black spots with uneven or feathery edges on leaves
  • Leaves turn yellow around spots
  • Leaves fall off
  • Sometimes reddish purple or black blisters on canes
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  • Image: Rose Streak 1
  • Image: Rose Streak 2

Rose Streak
Rose Streak Virus

  • Symptoms are most common on roses with large clusters of small flowers
  • Symptoms may vary in other cultivars
  • Leaves turn yellow and may have random dead brown spots
  • Leaves fall off in the spring or early summer
  • Very susceptible cultivars have brown to black streaks on the canes
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  • - NO PHOTO AVAILABLE -

Verticillium Wilt
Verticillium dahliae and Verticillium ablo-atrum

  • Tips of young canes wilt
  • Leaves turn yellow, then brown and then fall off
  • Damage starts on the lowest leaves first and then moves upward
  • Canes die and turn brown from the tip down
  • Purplish black streaks occur on stems before they dieback

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