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Purple Blotch

Severe leaf infection (Photo D. Pop) & Leaf symptoms (Photo M. Garnett)

Pathogen

Fungus

Hosts

Onions and Leeks

Symptoms

Spores infect the leaves to produce elliptical lesions which develop a purplish center and a yellow halo around the outside. These lesions can be several centimetres in length. Under severe disease pressure whole leaves can dieback prematurely. Sporulation leads to the formation of concentric rings.

Development

The lesions can encircle a leaf or stem leading to premature leaf/stem death. Spores can be washed down to the neck area of the bulb giving rise to a watery rot of the outer bulb scales. Spores can also be dispersed by wind. Overwinters on infected plant debris.

Favourable Factors

Warm, humid weather.

Importance

A disease of leeks, onions and chives. Losses arise during bulb storage. Can result in reduced yields with smaller bulbs.

Control

 

Identification and Management of onion and leek diseases

Find out more information on the key disease threats to your onion and leek crop. For each disease you will find out the importance of the disease in terms of potential yield penalty, how to identify the disease in its early stages and our advice on the best control strategies.

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