Purple blotch on onions
2008
Bulajic, A.R., Univerzitet u Beogradu, Beograd - Zemun (Serbia). Poljoprivredni fakultet
Purple blotch is economically very important disease of onions wherever grown. Disease is caused by plant pathogenic fungus, Alternaria porri. The symptoms usually begin as minute white spots which develop in elongate purple areas on the leaves. After 3-4 weeks the leaves collapse and infection can spread to the bulb causing a deep yellow to reddish watery rot. The scales become desiccated and dark. Bulbs may be small or fail to develop. The pathogen is carried over from season to season in crop debris and by seed. Purple blotch is controlled by cultural measures, like crop rotation, sanitation, balanced fertilization and regulating water regime, as well as by applyng fungicides when needed.
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