Acroconidiella tropaeoli. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Acroconidiella tropaeoli. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Tropaeolum spp. DISEASE: Causes severe losses in nasturtium seed fields in coastal California. It produces a yellowing and death of the leaves after mid season and this reduces yield. The fungus occurs sometimes on stems and is present on seeds but is most abundant on leaves where it forms characteristic irregular or subcircular brownish or purple spots visible on both sides. These are up to 1 cm diam. or often larger through confluence, the centres later shrivel and the surrounding tissues may form a broad yellow margin. GEOGRAPHICAL DISTRIBUTION: Argentina, Australia, Ceylon, Ethiopia, Guatemala, Haiti, India, Jamaica, Kenya, Mauritius, New Guinea, New Zealand, Tanzania, Uganda, U.S.A. TRANSMISSION: The pathogen is borne internally and externally in up to 93% of commercial nasturtium 'seed', persisting for at least 3 years in the form of thick-walled mycelium in the pericarp and seed.