| Causal agent: |
Ramularia beticola |
| Symptoms: |
Larger, not regular circular, sometimes even angular leaf spots (4-10 mm in diameter), brighter and more irregular margins than with Cercospora, their centres are silvery grey to white in colour. The tissue in the inner spots dies and may become brittle. Under the magnifying glass a white mycelium is visible in isolated spots on moist leaves. |
| Epidemiology: |
The fungus survives on dead leaves and in the soil, so that the potential for infection increases with a close crop rotation. Symptoms become apparent after 18 days at temperatures ranging from 17 to 20° C and a relative humidity of more than 95 %. The infection occurs under wet weather conditions. The distribution of the spores takes place through wind and rain splash. |
| Risks: |
Risk of infection is increased by close rotations and by the use of irrigation. |
| Economic importance: |
The pathogen appears in all sugar beet growing areas. Very early attacks, often accompanied by other diseases can totally destroy the crop's foliage (uncommon in UK). The subsequent regrowth of new leaf severely reduces sugar content. |
| Control: |
Fungicides are available to combat the disease. However the choice of resistant varieties is the most cost effective solution. |
