Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 4/7/2004
Publication Date: 8/1/2005
Citation: Phytopathology 95:S155
Technical Abstract: Yellow starthistle (Centaurea solstitialis L., YST), an invasive weed in California and the western U.S., is targeted for biological control. In 2003, an epidemic of dying YST plants was found near Kolzani, Greece. Diseased YST plants were sent to the Foreign Disease Weed Science Research Unit, USDA/ARS, Ft Detrick, MD where the causal organism of the disease was isolated. Based on culture characteristics, fungal morphology and ITS sequence the organism was identified as Cladosporium herbarum. Rosettes and bolted YST plants were inoculated with spores of the fungus and placed in a chamber with 8 hr dew and 12 hr light daily. Plants in the rosette stage were resistant, but the fungus was very aggressive on bolted plants. Within 4-6 days of inoculation necrosis developed on leaves and stems and then spread to capitula, often resulting in plant death. The fungus was also aggressive on developing flowers. The fungus was reisolated consistently from plants in two separate tests. Results of host range tests will establish if this isolate of C. herbarum has potential as a biological control agent of YST in the USA.