Scientific name Various
Plants affected Pansies
Main causes Fungus and fungus-like (Oomycete) organisms
Timing Winter until early summer
What are pansy leaf spots?
Spots and blotches on the leaves of pansies are caused by the fungal pathogens Ramularia lactea, R. agrestis and Mycocentrospora acerina.
Pansies also suffer from downy mildew caused by the fungus-like (Oomycete) organism Peronospora megasperma.
Symptoms vary, depending on the disease that is to blame;
- Dark greasy spots appear on the leaves, becoming brown in the centre
- Pale tan spots and blotches similar to chemical scorch appear on the leaves
- Very dark blotches appear on the leaves and stems, and the crown of the plant may rot
- Yellowish blotches appear on the upper leaf surface, corresponding to a grey, fuzzy, fungus-like outgrowth on the lower surface
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- Avoid repeat planting on the same site to prevent build-up of these pathogens in the soil
- Unlike those of downy mildew, spores of the leaf spot fungi are not wind-borne over long distances. Be aware that the most likely orginal source of the leaf spot fungi is, therefore, plants that are already infected when purchased. Do not buy plants that show any signs of leaf spot
- Wild pansies and violets may be sources of infection for garden pansies
The fungicide tebuconazole with trifloxystrobin (Provanto Fungus Fighter Plus, Toprose Fungus Control & Protect) has a recommendation for the control of leaf spots on ornamental plants. Additonally, the fungicides tebuconazole (Provanto Fungus Fighter Concentrate) and triticonazole (Fungus Clear Ultra) are labelled for the control of other diseases on ornamental plants, and could therefore be used legally on pansy (at the owner’s risk) to try and control the leaf spotting. None of these fungicides will control downy mildew.
Inclusion of a fungicide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)
All of these pathogens produce spores on the affected parts of the leaf. The spores are spread by rain over short distances (leaf spots) or by wind over long distances (downy mildew). Mycocentrospora acerina and Peronospora megasperma also produce tough resting structures in the dead tissues which can contaminate the soil for several years, and the Ramularia species probably also do this.
The Ramularia species and Peronospora megasperma only infect pansies and violets, but Mycocentrospora acerina affects a wide range of plants and also causes a storage rot in carrots.
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