Rudbeckia auriculata Infected with a Pollen-mimic Fungus in Alabama

The fungus Fusarium semitectum infects the flowering heads of Rudbeckia auriculata at two sites in Alabama. This is the first report of a fungal agent infecting this globally rare species. The fungus produces orange-tinged or pinkish-white spores on the flower heads and renders infected flowers ster...

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Bibliographic Details
Published in:Southeastern naturalist (Steuben, Me.) Me.), 2006-03, Vol.5 (1), p.103-112
Main Authors: Diamond, Alvin R., El Mayas, Hanan, Boyd, Robert S.
Format: Article
Language:English
Subjects:
Andrena
Bees
Flowers
Fungal spores
Fungi
Fusarium
Fusarium semitectum
Infections
Insect pollination
Insect vectors
Plants
Pollen
Rudbeckia auriculata
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Summary:The fungus Fusarium semitectum infects the flowering heads of Rudbeckia auriculata at two sites in Alabama. This is the first report of a fungal agent infecting this globally rare species. The fungus produces orange-tinged or pinkish-white spores on the flower heads and renders infected flowers sterile. Fungal spores superficially resembled pollen and are picked up by the main pollinator, the composite specialist bee Andrena aliciae, which serves as a dispersal agent for the fungal pathogen. Fungal spores were found attached in higher ratios in those areas of the bee's body that come into most direct contact with the flowering heads during feeding. The rate of spread of the fungus on potted plants indicated significant negative correlations between number of infections and the distance from the fungal source. Fusarium colonies were isolated from the entire length of flowering stems, and apparently invade vegetative portions of the plants. As R. auriculata is a perennial plant that reproduces almost exclusively by the production of short stolons, the fungus poses no serious threat to its immediate existence.
ISSN:1528-7092
1938-5412
DOI:10.1656/1528-7092(2006)5[103:RAIWAP]2.0.CO;2