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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Prunus > Unusual growth on trunk or branches

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Prunus > Trunk/Branches > Unusual growth on trunk or branches

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  • Image: Black knot 1
  • Image: Black knot 2
  • Image: Black knot 3

Black knot
Apiosporina morbosa

  • Lumpy olive to black elongate swellings along all sizes of twigs
    and branches
  • Gall formation may cause leaves to wilt or not leaf out showing branch dieback
  • Rough black cracked swelling can occur on the main trunk
  • Most common on choke and pin cherry
  • More information on Black knot
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  • Image: Crown Gall 1
  • Image: Crown Gall 2
  • Image: Crown Gall 3

Crown Gall
Agrobacterium tumefaciens

  • Galls, a large rough woody growth, form on roots or at the base of the trunk
  • Galls are light colored when young, and turn dark brown to black, rough and cracked with age
  • Growth of young plants with several galls is stunted
  • Infected plants more susceptible to drought stresses or winter injuries
  • More information on Crown Gall
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  • Image: Mechanical damage 1
  • Image: Mechanical damage 2
  • Image: Mechanical damage 3

Mechanical damage

  • Areas of bark are missing from stem or branches
  • If bark removal encircles stem or branch, thinning canopy or branch dieback will be seen
  • Leaves are undersized and yellow
  • Rubbery sap exudes from openings or wounds called gummosis
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  • Image: Scurfy scale 1

Scurfy scale
Chionaspis furfura

  • Infested twigs and branches show dieback in canopy
  • Adults are white and covered by a white cocoon-like armor, which gives the appearance of white bumps along the stem or branches
  • Crawlers or juvenile scales are light purple
  • Cocoon-like armor can be seen year round but crawlers can be seen in June
  • More information on scale insects

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