Pyracantha (Firethorn)-Scab

Cause Venturia inaequalis (formerly Spilocaea pyracanthae), a fungus that overwinters in infected leaves, twigs, and berries. No ascigerous state has been identified. Hosts are evergreen, but only young leaves and berries are most susceptible to infection. Rain splashes spores to young, emerging leaves and flower buds in the spring. Conidia, produced in lesions, are also spread during wet weather to healthy portions of the plant. Wet weather favors disease development. Apple scab will not infect pyracantha and isolates from pyracantha will not infect apple.

Symptoms Similar to apple and pear scab with olive-green to black spots on leaves, twigs, and fruit. Heavily infected leaves may yellow or redden and fall off prematurely. Fruit can be completely covered with cracked, scabby, dark lesions.

Cultural control

  • Prune in the dormant season to remove dead wood and foliage.
  • Some cultivars are resistant to scab, fire blight, and frost Yellow berries-'Shawnee', P. atalantoides, 'Aurea'. Orange berries-'Mohave', 'Orange Glow', 'Teton' (pyramid-type). Red berries-P. rogersiana, 'Watereri', 'Government Red', 'Navaho'.
  • Rake and destroy fallen leaves and fruit.

Chemical control Spray in spring when buds begin to swell and again 2 to 3 weeks later.

  • Copper-Count-N at 1 quart/100 gal water. 48-hr reentry.
  • Daconil Weather Stik at 1.4 pints/100 gal water. Group M5 fungicide. 12-hr reentry.
  • Eagle 20 EW at 6 to 12 fl oz/100 gal water. Group 3 fungicide. 24-hr reentry.
  • Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
    • Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
    • Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
  • Monterey Liqui-Cop at 3 Tbsp/gal water. H
  • Nu-Cop 50 DF at 1 lb/100 gal water. Group M1 fungicide. 48-hr reentry.
  • Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
  • Propiconazole-based products. Group 3 fungicides.
    • Banner MAXX at 5 to 8 fl oz/100 gal water. 12-hr reentry.
    • ProCon-Z at 5 to 8 oz/100 gal water. 24-hr reentry.
  • Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 fungicide. H
  • Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
  • Thiophanate-methyl-based products. Group 1 fungicides. 12-hr reentry.
    • Cleary's 3336 EG at 12 to 16 oz/100 gal water.
    • OHP 6672 4.5 F at 10.75 to 20 fl oz/100 gal water.
    • Systec 1998 at 20 fl oz/100 gal water. Washington Only.
  • Tourney 50 WDG at 1 to 4 oz/100 gal water. Group 3 fungicide. 12-hr reentry.
  • Trigo at 3 to 9 oz/100 gal water. Group 3 + 11 fungicide. 12-hr reentry. Wettable sulfur at 3 teaspoons/1 gal water. Group M2 fungicide. H O

References Le Cam, B., Parisi, L., and Arene, L. 2002. Evidence of two formae speciales in Venturia inaequalis, responsible for apple and pyracantha scab. Phytopathology 92:314-320.

Vassey, W.E., Gould, C.J., and Ryan, G.F. 1977. Disease-resistant pyracantha for the Pacific Northwest. Ornamentals Northwest 1(18):4-6.