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Carrot black rot

Scientific Name
Alternaria radicina
Scientific Author
(Meier) Drechsler & E.D. Eddy
Taxonomy
(Deuteromycotina: Hyphomycetales: Dematiaceae)
Status
Exotic Species Occurrence in Australia
Reliability
High
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Diagnostic Images

Host Symptoms
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Caption
Alternaria radicina collar infection of 6-8 week old carrot seedlings
Source
Robin Coles Rural Solutions South Australia
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Diagnostic Images (5)
Diagnostic Notes

Alternaria radicina is a seed-borne pathogen and causes carrot losses due to poor seedling establishment and damping-off. This disorder occurrs unpredictably, usually during periods of warm humid weather and has not been controlled successfully by fungicides such as thiram and iprodione applied as a seed coating. The fungus can also be soil-borne and can infect carrots at any stage of growth.

Carrots that survive early infection by A. radicina frequently develop a black ring of decay around the top of the stem and this reduces carrot quality. Older plants are particularly susceptible . Senecing leaves are often infected first, followed by infection of the crowns, that may lead to necrosis of the upper portion of the storage root. Late in the growing season the the base of the petioles turn dark brown to black and eventually the leaves are killed. This causes the stem tissue to breaks during mechanical harvesting.

The disease can cause significant losses in seed crops where both roots and umbels might be infected. Untreated imported carrot seed has been found to have A. radicina infestations of up to 35%.

The high incidence of A. radicina on imported carrot seed shows that the pathogen is common in many of the carrot seed-producing areas of the world.

More Information
Specimen Contact
Robin Coles
Author
Coles, R.
Created
21/02/2006 02:45 AEST
Last Updated
08/04/2010 17:09 AEST
Citation
Coles, R. (2006) Carrot black rot (Alternaria radicina ) Updated on 4/8/2010 5:09:49 PM Available online: PaDIL - http://www.padil.gov.au.
Image Use
Free for use under the Creative Commons Attribution 3.0 Australia License

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