page_title: List of pests and diseases of roses
section_title: Fungal diseases
hierarchical_section_title: List of pests and diseases of roses / Diseases / Fungal diseases
caption_attribution_description: Rose Mildew - Podosphaera pannosa
context_page_description: Roses are susceptible to a number of pests, diseases and disorders. Many of the problems affecting roses are seasonal and climatic. Some varieties of roses are naturally more resistant or immune than others to certain pests and diseases. Cultivation requirements of individual rose species and cultivars, when observed, often assist in the prevention of pests, diseases and disorders.
context_section_description: Black spot (class Leotiomycetes: family Helotiales) Diplocarpon rosae syn. Marssonina rosae – Marssonina rosae causes black spots on leaves. The spots, which may be as much as 12 mm across, are generally circular and have an irregular edge often with a yellow halo. Leaves frequently turn yellow and fall early. Sometimes new leaves are produced, and these may also become affected. Continual defoliation will cause weakness, dieback or death of the plant. Some very susceptible species may have stems affected with a considerable reduction in plant vigour.
  Powdery mildew (Podosphaera pannosa) – P. pannosa produces a very fine, powdery coating on the surface of buds and leaves. Significant cases have stems and particularly thorns, infected. Attacks on young leaves and buds will cause deformity with retardation of growth. Infected buds will fail to open. The disease is likely in hot, humid weather, with fungal spores overwintering on the stems and fallen leaves.
  Downy mildew (class Oomycetes: family Peronosporaceae) Peronospora sparsa – Peronospora causes purple-red to dark-brown spots with irregular margins on the leaves, however, often angular. Stems, petioles and flower stalks can split and spotted with purple marks. Buds, sepals, petals and calyces can be affected and will present purple spots. New growth affected will be deformed. The disease is spread by wind.
  Rust  Phragmidium mucronatum – Rose rust appears as yellow patches on the surface of leaves, with orange pustules of spores underneath the leaf. The fungus is spread by wind. Affected leaves fall prior to healthy ones and plants may be defoliated in serious infections.
  Anthracnose Sphaceloma rosarum – Spots caused by this fungus originate from a point where leaves are water soaked, usually unnoticeable at first, until they turn black with a very distinct defined edge. As the spots enlarge the centre becomes grey and may fall out resulting in a shot-hole appearance. Defoliation may occur but is often not serious.
  Grey mould (class Leotiomycetes: family Sclerotiniceae) Botrytis cinerea – On roses grey mould is primarily a disease of the flowers and buds, leaves are infrequently attacked. Infected buds rot on the stem and infection may progress down the stem. On petals Botrytis cinerea produces pink rings.
  Verticillium wilt (class incertae sedis: family Verticillium) Verticillium dahliae
  Sooty moulds Alternaria species – Sooty mould appears as black, dry powder on leaves similar to chimney soot. Many sooty moulds grow on the honeydew (frass) produced by sap-sucking insect such as aphids and soft scales. Alternaria does no direct damage to plants but surface cover of leaves will reduce the plants capacity to photosynthesise and may create an unsatisfactory plant appearance.
  Canker Leptosphaeria coniothyrium and Cryptosporella umbrina – Cankers present as small yellowish or reddish spots on bark slowly increasing in size. Leptosphaeria coniothyrium turns brown, increases in size, and may eventually girdle the stem. The tissue within the infection begins to dry out and shrink, presenting a shrivelled appearance. If the disease infects only part of the stem, growth above the canker will continue. If it girdles the stem, however, growth will cease and the stem will die.
caption: Powdery mildew (Podosphaera pannosa)
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