Beet cercospora disease

Beet cercospora disease is a disease caused by the fungal pathogen Cercospora beticola. The fungus thrives in warm, humid conditions. It is often caused by diseased seeds or planting materials and promoted by poor air flow, low sunlight, overcrowding, improper soil nutrient and irrigation management and poor soil drainage. The symptoms can be easily confused with bacterial blight of sugar beet.

Symptoms
Small leaf spots (4-5mm diameter) with grey necrotic center and red margins. The spots develop and multiply causing severe dehydratation of the lamina starting with the marginal leaves and progressing to the destruction of the entire crop foliage. Black microscopic fructifications occur on the leaf spots on the abaxial surface. The decay of the foliage and the new shoots the plant puts forth in response to the disease cause important loss of weight and sugar quality. The seed crops are also invaded by spots from the base of the plant up to the bracts and seeds. Stromata (black dots about the size of pepper grains) form during humid weather in leaf spots on sugarbeet debris or newly infected leaves; they are easily seen with a hand lens. When weather is warm and wet, stromata produce silver or steel-gray spores which gives the leaf spot a fuzzy appearance.

Control

 * Remove and destroy infected plants and bury leaf debris by tillage.
 * Practice crop rotation; avoid planting within 90m (100yds) of an infected sugarbeet field from the previous year. Plant to non-host crops for at least two successive seasons.
 * Use diseased-free seeds or use resistant cultivars.
 * Observe proper planting distances and maintain sanitation by removing a disposing of infected plant materials.
 * Avoid working when plants are wet.
 * Apply fungicides judiciously (monitor for disease and conditions favorable for disease). Alternate different classes of fungicides to avoid development of resistant strains of Cercospora.