Diseases & Disorders

Helpful advice on what to do when problems strike, whether they're diseases, disorders or otherwise - and how to prevent them occurring

phytophthora

Fungal infection

Phytophthora is our second most reported disease. Causing die-back and leaf damage on trees and shrubs and is often fatal.

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  • Pocket plum. Image: RHS, Horticultural Science

    Pocket plum

    Pocket plum is a fungal infection of the young fruits of plums, damsons and some ornamental species, causing them to develop abnormally, without stones.

  • Quercus showing poor autumn colour. Image: RHS Advisory

    Poor autumn colour

    Autumn produces some of the most vibrant colours of the year in the leaves of deciduous trees and shrubs. However, autumn colour can vary from year-to-year, and between individual trees and shrubs of the same species. This can be due to reasons such as the weather.

  • Close up of tomato blight at RHS Garden Wisley. Image: RHS/John Trenholm

    Potato and tomato blight

    Potato and tomato blight, properly called late blight, is a disease of the foliage and fruit or tubers of tomatoes and potatoes, causing rotting. It is most common in wet weather.

  • Potato black scurf and stem canker

    Potato black scurf and stem canker

    Black scurf is a fungal disease that causes black patches on the surface of tubers that can be rubbed off. Although unsightly it is not destructive, but infected seed potatoes can lead to plants with stem cankers.

  • Healthy potato (left) and one infected with potato blackleg (right). Image: RHS, Horticultural Science

    Potato blackleg

    Potato blackleg is a common bacterial disease of potatoes, which causes black rotting at the stem base. Initial infections cause stunted growth and yellowing stems.

  • Common potato scab. Image: RHS, Horticultural Science

    Potato scabs

    Common scab and powdery scab are bacterial and fungal diseases of potato skins, causing rough, scabby patches.

  • Black leg (Pectobacterium atrosepticum) on potato 'Charlotte'. Credit: RHS/Pathology.

    Potato tuber rots

    A number of fungi and bacteria are capable of causing decay in potato tubers. Symptoms are often present at lifting, but some of the problems will also spread through stored tubers, and a few will only develop after prolonged storage.

  • Powdery Mildew

    Powdery mildews

    Powdery mildews are a group of related fungi which attack a wide range of plants, causing a white, dusty coating on leaves, stems and flowers.

  • Leaf spot on Primula species. Lower (left) and upper (right) leaf surfaces. Image: RHS, Horticultural Science

    Primula leaf spots

    Leaf spots on primulas are yellow spots, often with dead, brown centres, and are caused by several different fungi.

  • Pyracantha scab on berries. Image: RHS, Horticultural Science

    Pyracantha scab

    Pyracantha scab is a fungal disease of the blossoms, leaves and fruit of Pyracantha, resulting in leaf fall, loss of flowers and disfigured fruit.

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