Why Does My Horseradish Look Sickly?

Are there any small translucent spots on leaves, spots later turn black?

Does the plants have poor growth with brittle, discolored roots, and chlorotic leaves that collapse and dry out?

Do the leaves have round or angular tan spots with lighter centers?

Are there any yellow-green circular patches between leaf veins that later turn into distinct lesions with irregular margins?

Are there any pale yellow areas on upper leaf surfaces followed by the appearance of creamy white pustules on the underside of the leaves?

Is there any green and yellow mottling on leaves, and black streaks on petioles?

Are there large or small holes in leaves, damage may be extensive?

Are the leaves riddled with small holes?

Bacterial leaf spot causes circular translucent spots scattered over the leaf surface between the veins. These spots turn brownish-black and may spread to form large patches of dead tissue. To prevent the spread of this disease, avoid working around wet plants. Remove and destroy affected parts. Spray Bordeaux mix on remaining plants.

Disease called Brittle rot is caused by bacteria transmitted by beet leafhoppers and is one of the most destructive diseases of horseradish. Control leafhoppers with early detection and application of insecticidal soap or pyrethrin.

These spots are caused by fungal disease - Cercospora leaf spot. This fungal disease only occurs in very warm climates. Spots develop a “frog-eye” appearance with light centers and dark edges. Spray plants with copper as soon as symptoms appear to prevent further symptom development.

Ramularia leaf spot is caused by a fungus that overwinters on plant debris. Remove weeds and any horseradish debris from around plants. Avoid the use of sprinklers for irrigation. Remove and destroy any infected plants to prevent spread. If the disease is problematic it may be necessary to treat them with copper fungicides.

If there are pale yellow areas on upper leaf surfaces and white blisters on the undersides of the leaves the culprit is a fungal disease White rust. Disease development is favored by cool weather and periods of extended rainfall. Destroy infected leaves or plants. Remove weeds and any horseradish debris from around plants. Avoid the use of sprinklers for irrigation. Thin plants to increase airflow.

Mottled leaves and black streaks on petioles are caused by Mosaic virus. Viral diseases are incurable. Horseradish can tolerate low levels of infection, but heavily infected plants should be destroyed.

Cabbage looper is a pale green caterpillar with white lines running down either side of their body. Looper populations are usually held in check by natural enemies, but if they do become problematic larvae can be hand-picked from the plants. The application of BTK will effectively kill younger larvae.

Small holes in leaves are caused by Flea beetles. These tiny, black, brown, or bronze beetles hop when disturbed. Larvae are small and white, feed mostly on the undersides of leaves. Prevent problems by covering young plants with row cover. Control severe infestations by spraying or dusting plants with pyrethrin.

If your plants have pale leaves and stunted look the culprits may be leafhoppers. Treat infested plants with insecticidal soap in the evening or with a commercial pyrethrin spray or dust if the infestation is severe.