Damping-off disease destroys seedlings in cold, wet soils. Be careful not to drown young plants, and time planting to when soil is warm.
Snails and slugs love beetroot seedlings. Cover with upturned pots at night or use pet-safe snail bait.
Cercospora leaf spot disease (left) is common in warm, wet weather, causing grey spots with reddish borders. Remove and destroy affected leaves, and avoid wetting foliage.