| Date | 1833 |
| Author | Unger |
| Contribution | Published claim that parasitic fungi of plants arise from morbid sap. |
| Reference | Ainsworth |
| Notes | Given as example of opposition of even eminent botanists such as Franz Unger to germ theory of these diseases. Fungi were effects not causes. See Prevost,1807 and others. |
| Category | Causation |
| Pathogen Class | Fungi |
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