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Black Knot

Description:

  • 1st year - soft greenish knots or elongated swellings on twigs & branches
  • 2nd year - become black, corky, cylindrical galls
  • 13mm - 38mm in diameter, 31cm in length
  • beyond galls usually stunted, may die
  • galls appear 6 months after infection

Cause:

  • fungus

What it Attacks:

  • various species of cherries
  • other ornamentals & fruit trees
  • very damaging to plums
    • most susceptable:
    • Bluefre, Damson, Shropshire, Stanely
    • moderately susceptable: Bradshaw, Early Italian, Fellenberg, Formosa, Methley, Milton, Santa Rosa, Shiro
    • most resistent: President

Prevention/Control:

  • disease spreads fastest in warm wet weather
  • prune out & destroy infected twigs & branches during fall/winter
  • cut at least 10cm below visible signs of infection
  • cut knots out of trunk and large branches at least 13mm past diseased tissue
  • lime sulfur
  • garden sulfur
  • For suggestions on chemical control of this disease, see the Pesticides section under Gardeners.
Black Knot

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