Comfrey pests and diseases

Comfrey rust (Melampsorella symphyti) is identified by spores on leaves appearing as orange yellow dust or spots. These are found on the underside of the leaves in early summer. Plants will be stunted and have pale coloured leaves.

Cut back any plants that shows signs of comfrey rust. Add a high potassium feed such as compost, manure or wood ash. This will help the plants 'grow away' from the disease. Badly affected plants should be removed and destroyed, and when propagating new plants do not use any that show signs of rust.

Comfrey rust is not the same rust that appears on broad beans (Uromyces viciae-fabae) so this will not affect other plants.

Comfrey mildew is seen as white patches or a white layer on leaves and stems.

Mildew is more common on wild comfrey and tends to occur on older leaves at the end of the season when plants are less vigorous.

Strong, vigorous plants will be less susceptible to disease, so aim to keep your plants well fed, adequately spaced, and regularly cut and watered. Comfrey mildew can infect some ornamentals in the borage (Boraginaceae) family.