What is wrong with my celeriac?

Are the seedlings dying and the stems are girdled or rotted at the soil line?

Do the leaves of your celeriac have dark, yellow-bordered spots on them?

Are the leaves yellow, the plant is stunted and veins in the stalks are reddish?

Are the leaves yellow and mottled, stalks are twisted and the plant is dwarfed?

Do the leaves and stalks have irregular tan spots on them?

Are the leaves yellow, curled, and wilted?

Do the leaves turn yellow and then brown from the bottom up, the plant loses vigor and appears stunted?

Do the leaves have tunnels or blotches in them?

Do the leaves have large, ragged holes in them?

Did the central leaves turned dark?

Do the leaves have chewed holes in them or rolled edges?

If your seedlings are falling over and the stems are girdled or rotted at the soil line, the most likely cause is a damping-off disease. Remove and destroy all infected plants. To prevent damping-off let the soil surface dry between waterings, thin seedlings to avoid overcrowding, and do not add nitrogen fertilizers until plants have developed leaves.

Two fungal blight diseases attack celeriac (Cercospora blight and Septoria blight). Stalks of afflicted plants may also develop spots or dark areas. Destroy spotted leaves. Spray plants with copper if symptoms are serious.

These symptoms usually indicate Fusarium yellows. This fungal disease is incurable. Destroy all plants with symptoms, and do not compost them.

Celery mosaic is a viral disease that affects celeriac. It is incurable. Destroy infected plants immediately. Control aphids because they can spread viral diseases as they feed. Prevent problems by planting resistant cultivars.

Brown spot is a fungal disease that causes these symptoms. Control this fungal disease by spraying plants with Bordeaux mix when spots appear to prevent further spread.

Yellow, curled, and wilted leaves on celeriac usually indicate aphids. These tiny insects vary in color, green, pink, black, gray to completely white. You can control them by washing them off the plant with water spray. Insecticidal soap or neem oil should be used only with severe infestations.

Wireworms are the soil-dwelling larvae of click beetles. They look like wiry-jointed worms. Check the soil before planting and flood the soil if wireworms are present. Remove infected plants and surrounding soil.

Leafminer larvae tunnel inside leaves. Destroy infected leaves and caterpillars. Cultivate the garden to destroy larvae and keep adult flies from laying eggs. Cover crops with floating row cover to exclude flies.

Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves usually at night. To control slugs and snails use diatomaceous earth around your plants. You can also handpick them during the night or use shallow dishes filled with beer as a trap.

Tarnished plant bugs inject a plant-deforming toxin as they feed on young leaves. Trap them with white sticky traps or treat plants with a commercial pyrethrin spray or dust in the evening to control severe infestations. The best way to prevent this pest is through a thorough fall and spring cleanup. This will prevent it from overwintering.

Various caterpillars attack celeriac, the most prominent is Celery leaftier. You can handpick and destroy them if the infestation is not severe. BTK spray will help in controlling caterpillars.

If the stalks or crowns of your celeriac are rotted the most likely cause are Bacterial and fungal rots. Various bacteria and fungi will rot celeriac stalks and crowns. Destroy infected plants. Spray remaining plants with copper. Prevent problems by controlling insect pests, such as carrot rust flies, that injure roots, creating openings for disease organisms.