Cercospora Leaf Spot
Disease · Commonly affects: Table beets, Swiss chard, Spinach, Peppers, Carrots, Celery
Cercospora leaf spot is a common fungal disease caused by fungi in the genus Cercospora, most familiar to gardeners on beets and chard as Cercospora beticola. It matters because it thrives in the warm, humid weather of much of the US growing season and can strip the leaves off an otherwise healthy plant, cutting into both harvest and quality.
How to identify it
Look for many small, round spots on the leaves, usually about the size of a pinhead up to a quarter inch across, with pale tan or gray centers ringed by a reddish-purple or dark brown border. As spots age their thin centers often dry out and fall away, leaving a ragged, shot-hole look, and in damp weather you may see tiny dark specks in the center of each spot. Spots typically start on older, lower leaves first and multiply upward, sometimes merging into larger blighted patches when infection is heavy.
Damage
By killing leaf tissue spot by spot, the disease reduces the green area a plant needs to feed itself, and severe cases cause older leaves to yellow, collapse, and drop early. This loss of foliage stunts growth and lowers yield: beets size up poorly, and the outer leaves of chard, spinach, and other greens become spotted and unmarketable.
Prevention
Rotate host crops so beets, chard, and their relatives do not return to the same bed for two to three years, since the fungus survives winter on leftover plant debris and in soil. Give plants generous spacing and full sun so leaves dry quickly after rain or dew, choose resistant or tolerant varieties and certified disease-free seed when available, and build healthy, well-drained soil that supports vigorous growth. Clean up and remove old leaves, culls, and weedy relatives such as wild beet at the end of the season rather than leaving them in the garden.
How to manage it
At the first sign of spots, pick off and discard the affected lower leaves, and thin or prune crowded plants to open them up so air moves freely and foliage dries fast. Water at the base of the plant early in the day instead of wetting the leaves overhead, and stay out of the beds while plants are wet so you do not carry spores from plant to plant. Keep the area weeded and remove diseased debris promptly; put badly infected material in the trash rather than the compost pile to avoid carrying the fungus over to next season.
General guidance for US home gardens, focused on prevention and non-chemical control. For a confirmed diagnosis and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.