| Host genus | Fungal species | Symptoms and notes |
| Gagea | Vankya ornithogali | Conspicuous smut affecting living leaves |
| Galega | Erysiphe galegae | Powdery mildew of leaves |
| Galeopsis | Neoerysiphe galeopsidis | Powdery mildew of leaves |
| Geranium | Coleroa circinans | On living and moribund leaves of a range of Geranium species (apparently not G. robertianum) |
| Coleroa robertiani | Biotrophic on living leaves of G. robertianum, apparently causing little or no damage | |
| Uromyces geranii | Rust on leaves of many species | |
| Geum | Podosphaera aphanis | Powdery mildew of leaves |
| Glyceria | Claviceps purpurea | Infects inflorescences causing ergots. Hghly toxic. |
| Ustilago filiformis | Causes stripe smut of leaves | |
| Goodyera | Pucciniastrum goodyerae | Rust on leaves |