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Cercospora Leaf Spot

Cercospora leaf symptoms, Severely affected beet plants (Photo E. Crawford) & heavy disease pressure on leaf

Pathogen

Fungus

Hosts

Sugar Beet

Symptoms

The disease appears as small (2-3mm) round grey spots with reddish margins. Under humid conditions and with the use of a hand lens, black spots (spore producing structures) can be seen in the centre of the lesions, which helps to distinguish it from Ramularia.

Development

It usually appears on individual plants and can spread if temperature and humidity are both high. Under severe disease pressure the lesions coalesce to the extent that whole leaves can be lost. Overwinters as spores on old leaves and plant debris. Can also be seed-borne but this is thought to be a minor source of infection.

Favourable Factors

Although Cercospora develops above 17C under UK conditions it requires daytime temperatures of 25C or greater and high humidity for rapid spread.

Importance

In warmer climates where there are frequent storms or irrigation is used, Cercospora can cause severe damage resulting in a yield loss of as much as 50%. In the UK its future development will depend on summer weather conditions. The rapid spread of Cercospora infections across the Netherlands within 5 years suggests its development in the UK should be closely monitored.

Control

Identification and Management of sugar beet diseases

Find out more information on the key disease threats to your sugar beet 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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