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Ramularia Leaf Spot

Ramularia on a younger and older beet leaf (Photo J. Hill) & Ramularia (Photo R. Bradbury)

Pathogen

Fungus

Hosts

Sugar Beet

Symptoms

It appears first on older leaves as brown-grey spots with dark edges. Under a microscope or powerful lens, small white spots can be seen emerging through the stomata. Under humid conditions, similar looking spots occur on Cercospora infected leaves but are distinguished from Ramularia by their black colour. Other distinguishing factors for Ramularia are: The lesions:

Development

It is thought to overwinter on crop debris and can also be seed-borne.

Favourable Factors

Ramularia prefers cooler conditions than powdery mildew - around 17C - and infection only occurs when relative humidity exceeds 95% so it is mainly observed from September onwards.

Importance

It seldom causes significant yield losses in the UK unless it is so severe that leaves are lost and newly debeloping leaves use up accumulated energy from the root. Where disease pressure is severe sugar yield loss can be as much as 25%.

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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