| Causal agent: |
Peronospora farinosa |
| Symptoms: |
Grey fungal hyphae develop on the lower leaf surface. The infected leaves turn downward, are thickened and become discoloured on the upper leaf surface. The diseased leaves are retarded in growth. |
| Epidemiology: |
The infection is favoured by wet and cool weather conditions (high relative humidity and temperatures between 10 and 17° C). The disease may appear in early spring and recur in autumn. |
| Risks: |
Sources of infection may be volunteer and other overwintering beta species. Young seedlings are extremely susceptible. |
| Economic importance: |
The disease rarely occurs in commercial beet crops. |
| Control: |
Normally not required (copper products in seed crops). Fubol fungicide. |
