Cause Urocystis trillii, a fungus reported from Oregon and Idaho but considered a rare disease. This fungus is soilborne and infects plants as they emerge through the soil.
Symptoms Black lesions are seen to erupt from stems. These black structures are a compact aggregation of spores and/or sporophores called sori. The black sori are observed mainly on stems sometimes spreading to the base of leaves. Sori are large and confluent with individual sori reaching 1.5 inches in length.
Cultural control
- Rotating to different ground.
- Wash and then dry host material well before moving so that spores in the soil or on the plants are not also moved.
- Remove and dispose of diseased plants.
Chemical control This is usually done as a seed treatment for small grains but in this case it would be bulb or rhizome treatment. No chemicals are specifically registered for Trillium but the ones listed below are legal to try after testing for phytotoxicity.
- Postiva at 10 to 28 fl oz/100 gal water. Group 3 + 7 fungicide. 12-hr reentry.
Reference Henricot, B. 2010. New diseases of Trillium in the UK caused by Colletotrichum lineola and Urocystis trillii. New Disease Reports, 22:32.