| Host genus | Fungal species | Symptoms and notes |
| Salix | Cryptomyces maximus | Weak parasite of branches, sometimes correlated with mechanical damage |
| Linospora capreae | Implicated in development of leaf spots, but pathology uncertain | |
| Sanguisorba | Phragmidium sanguisorbae | Rust of leaves, causing minimal damage to the plant |
| Sasa | Apiospora sasae | Sporulating on conspicuous dead margins of leaves, but pathogenic status uncertain |
| Satureja | Puccinia menthae | Rust of leaves and stems |
| Scilla | Alternaria hyacinthi | Causes leaf spot and bulb scale damage to Freesia, Hyacinthus orientialis and Scilla peruviana |
| Cladophialophora scillae | On leaf spots and moribund leaves of Scilla peruviana | |
| Scorzonera | Puccinia scorzonerae | A rust on leaves |
| Secale | Claviceps purpurea | The ergot fungus, infecting inflorescences and forming sclerotia from modified seeds. Highly toxic |
| Senecio | Puccinia lagenophorae | Rust of leaves and stems, sometimes causing distortion of host tissues |
| Silene | Microbotryum silenes-dioicae | Infects anthers of S. dioica |
| Smyrnium | Puccinia smyrnii | Rust on leaves and stems |
| Solidago | Puccinia virgae-aureae | Rust of leaves |
| Sorbus | Leucostoma massarianum | Causes canker and dieback of twigs and young branches |
| Stachys | Neoerysiphe galeopsidis | Powdery mildew of leaves |