Prune and Plum (Prunus spp.)-Leaf Spots

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Cause Wilsonomyces carpophilus, also called shothole, is observed more frequently than Blumeriella jaapii (formerly Coccomyces prunophorae). Both fungi are favored by warm, wet conditions in spring.

Symptoms Both fungi produce small, purplish, circular spots that turn brown as they enlarge. Spots caused by shothole are generally larger. Often the spots' centers drop out, giving the leaf a shothole appearance.

Cultural control

  • Prune trees for good air circulation.
  • Rake and destroy leaves in home gardens.

Chemical control Tank-mix or alternate chemicals to prevent fungi from developing resistance. Limit the use of any one group during crop production. Selection of products for rotation and/or mixing must consider group 7 fungicides when used through the irrigation as a nematicide.

  • Spray at leaf fall in late autumn to control shothole.
    • Bordeaux 8-8-100. Group M1 fungicide. O
    • Bravo Weather Stik at 3.1 to 4.1 pints/A. Group M5 fungicide. 12-hr reentry. H
    • Copper-based products such as C-O-C-S, Cueva, Nu-Cop, Nordox, Cuprofix, or Kocide most with a 48-hr reentry. Group M1 fungicides. H O
    • Echo 720 at 3.1 to 4.1 pints/A. Group M5 fungicide. 12-hr reentry.
  • The following fungicides may be useful if applied at petal fall, shuck split, and 2 weeks later.
    • Abound at 12 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied the day of harvest. Sprayers should not be used on apples. Group 11 fungicide. 4-hr reentry.
    • Bonide Captan 50 WP at 1 to 1.5 Tbsp/gal water can be used in home gardens. H
    • Bravo Weather Stik at 3.1 to 4.1 pints/A. Group M5 fungicide. 12-hr reentry. H
    • Captan 80 WDG at 2.5 to 3.75 lb/A. Group M4 fungicide. 24-hr reentry. H
    • Cevya at 4 to 5 fl oz/A. May be used day of harvest. Group 3 fungicide. 12-hr reentry.
    • Eagle 20 EW at 2 to 3 fl oz/100 gal water for home orchards or landscape use. Can be applied up to the day of harvest. Group 3 fungicide. 24-hr reentry.
    • Echo 720 at 3.1 to 4.1 pints/A. Do not apply after shuck split. Group M5 fungicide. 12-hr reentry.
    • Flint Extra at 2.5 to 3.8 oz/A. Do not apply within 1 day of harvest. 'Concord' grapes may be injured if accidentally sprayed. Group 11 fungicide. 12-hr reentry.
    • Inspire Super at 16 to 20 fl oz/A. Do not apply within 2 days of harvest. Group 3 and 9 fungicide. 12-hr reentry.
    • Luna Experience at 6 to 10 fl oz/A. May be used day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
    • Luna Sensation at 5 to 7.6 fl oz/A. Do not use within 1 day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
    • Merivon at 4 to 6.7 fl oz/A. Do not use with EC or oil-based products. Only nonionic surfactants can be used within 14 days of harvest. May be used day of harvest. Group 7 and 11 fungicide. 12-hr reentry.
    • Microthiol Disperss (80% sulfur) at 10 to 20 lb/A. Do not use a spreader-sticker. 24-hr reentry.
    • Miravis at 5.1 fl oz/A. Can be used up to the day of harvest. Group 7 fungicide. 12-hr reentry.
    • Miravis Duo at 13.6 fl oz/A. Can be used up to the day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
    • Pristine at 10.5 to 14.5 oz/A. Can be used day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
    • Propiconazole-based fungicides are registered. Do not use on Stanley-type Plums earlier than 21 days before harvest. Group 3 fungicides. 12-hr reentry.
    • Bumper 41.8 EC at 4 oz/A. Limited to two (2) applications during bloom.
    • PropiMax EC at 4 fl oz/A. Limited to two (2) applications during bloom. Do not use within 10 days of harvest.
    • Tilt at 4 oz/A. May be used up to and including day of harvest.
      • Quadris Top at 12 to 14 fl oz/A. May be applied on the day of harvest. Group 3 + 11 fungicide. 12-hr reentry.
      • QuiltXcel at 14 fl oz/A. May be applied the day of harvest. Do not use on Stanley-type Plums earlier than 21 days before harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
      • Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 0.5 fl oz/gal water. May be applied up to the day of harvest. Do not use more than seven (7) times per season. Group 3 fungicide. H
      • Topguard at 14 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
      • Topguard EQ at 6 to 8 fl oz/A. Do not use with silicone surfactants or within 7 days of harvest. Sprayers should not be used on apples Group 3 + 11 fungicide. 12-hr reentry.
      • Topsin 4.5 FL at 20 to 30 fl oz/A plus another fungicide with a different mode of action. This is specifically registered for this disease. This material may kill earthworms, which help decompose infected leaves. May not be used within 1 day of harvest. Group 1 fungicide. 2-day reentry.

Reference Ogawa, J.M. and English, H. 1991. Diseases of Temperate Zone Tree Fruit and Nut Crops. University of California. p461.