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San Jose Scale

FAST FACTS - SCALE
by Nanette Londeree, Master Rosarian

SIGNS

  • Small, grayish to white, round to oval encrustations on canes, ranging in size from 1/8 to 1/4 inch (armored scale)
  • Orange, yellow, or brown elongated, fluted, white cottony egg sac attached to body (soft scale)

    SYMPTOMS

    Scale

  • Darkening of cane
  • Decline of plant health and vigor
  • Dieback of twigs or stems
  • Honeydew on leaves, canes; sticky, sooty mold on leaves and ants (soft scale only)

    CAUSE

  • Armored scales, Aulacaspis rosae (rose scale) and Quadraspidiotus perniciosus (San Jose scale)
  • Soft scale (cottony cushion scale), Icerya purchase

    OPTIMAL CONDITIONS

  • Roses that are not heavily pruned each year
  • Nut and stone fruit trees infected with the pest in the area; spread by wind from almond orchards (San Jose scale)
  • Cottony cushion scale on citrus, nandina, and pittosporum in the area

    TREATMENT

    Prevention:

  • Provide good growing conditions and cultural care to help roses be more resistant to scale
  • Monitor susceptible varieties of plants for infection and treat immediately
  • Maintain good garden sanitation, and dispose of any infected plant materials
  • Control ants
  • Limit use of insecticides that may harm beneficial insects
  • Garden to encourage natural enemies (parasitic wasps and flies; the vedalia beetle, Rodolia cardinalis

    Elimination:

  • Prune away and destroy infected canes
  • Apply horticultural oil spray after pruning in the winter; repeat spraying may be necessary

    GOOD GUY / BAD GUY?

  • Can be a bad guy if infestation is severe

  • The photos of Scale are by Baldo Villegas from the extraordinary website: http://members.tripod.com/buggyrose/irosepests.htm


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    Last Modified: 08/06/2013