Hollyhock (Alcea rosea)-Rust

Cause Puccinia malvacearum, a fungus that overwinters in basal leaves, which may live through the winter, or on plant debris. Teliospores in association with plant debris remain viable at least 4 months in soil. Fungal mycelium may overwinter in young shoots of the host. Pycnia, aecia, and uredinia are not known for this fungus. Many other plants in the malvaceae can be infected.

Symptoms Reddish, raised spots on leaf undersides. Spots darken late in the growing season (telia only). Stems can also have red pustules. If the disease is severe, leaves may dry up and hang down without falling off the plant.

Cultural control

  • Pick up and burn all infected plant parts at the end of the growing season and again in early spring.
  • During the growing season, keep infected parts picked off.
  • Remove other hosts like cheeseweed (Malva parviflora), Lavatera, Hibiscus, and other Malvaceae plants.
  • There are differences in cultivar reaction so select ones that are more resistant.

Chemical control Use with cultural control methods.

  • Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. Group 3 + 11 fungicide. 12-hr reentry.
  • Banner MAXX at 6 to 8 fl oz/100 gal water may be effective. Group 3 fungicide. 12-hr reentry.
  • Bayleton 50 T&O at 5.5 oz/275 to 550 gal water. Landscape only, not for use on plants for sale. Group 3 fungicide. 12-hr reentry.
  • Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H
  • Compass 50 WDG at 2 to 4 oz/100 gal water. Do not use organosilicate additives. Group 11 fungicide. 12-hr reentry.
  • Daconil Weather Stik at 1.4 pints/100 gal. Group M5 fungicide. 12-hr reentry.
  • Eagle 20 EW at 6 to 12 fl oz/100 gal water. Group 3 fungicide. 24-hr reentry.
  • Fame SC at 1 to 4 fl oz/100 gal water. Group 11 fungicide. 12-hr reentry.
  • Heritage at 1 to 4 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
  • Insignia SC at 3 to 6 fl oz/100 gal water. Do not use with organosilicate-based adjuvants. Use preventively only. Group 11 fungicide. 12-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.
  • Myclobutanil 20 EW T&O at 6 to 12 fl oz/100 gal water plus spreading agent. May observe a PGR effect. Group 3 fungicide. 24-hr reentry.
  • Pageant at 6 to 12 oz/100 gal water. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. 12-hr reentry.
  • Phyton 27 at 1.5 to 2.5 oz/10 gal water. Group M1 fungicide. 48-hr reentry.
  • ProStar 70 WG at 3 to 6 oz/100 gal water. Group 7 fungicide. 12-hr reentry.
  • Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
  • Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 funigicide. H
  • Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
  • Terraguard SC at 2 to 8 fl 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.

Reference Sivanesan, A. 1970. Puccinia malvacearum. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 265.