Diseases & Disorders

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


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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  • Runner beans can often fail to set pods due to a number of reasons. Image: Mike Sleigh/RHS

    Runner beans: failure to set pods

    Failure of runner beans to set pods is a surprisingly widespread problem, particularly early in the season. Attention to soil conditions can help increase the harvest.

  • Rust diseases

    Rust diseases

    The rusts are amongst the most common fungal diseases of garden plants. Trees, shrubs, herbaceous and bedding plants, grasses, bulbs, fruit and vegetables can all be affected. Rust diseases are unsightly and often (but not always) reduce plant vigour. In extreme cases, rust infection can even kill the plant.

  • Saprophytic fungi

    Saprophytic fungi

    Only a very small proportion of the thousands of species of fungi in the world can cause disease in plants or animals – these are the pathogenic fungi. The vast majority of fungi are saprophytic, feeding on dead organic material, and as such are harmless and often beneficial. Just occasionally, however, the growth of saprophytic fungi can be a nuisance to the gardener.

  • Sclerotinia disease. Image: RHS, Horticultural Science

    Sclerotinia disease

    Sclerotinia disease is a fungal infection of many vegetables and ornamental plants. The fungus lives for long periods in the soil. When infected, plants rot at the base and a white fluffy mould may grow on affected parts.

  • ©RHS WSYD0012523

    Sheep’s sorrel

    Sheep’s sorrel (Rumex acetosella) is a relative of dock whose tangy young leaves in long grassland are favoured by foragers. However, in gardens especially on sandy, acidic soils it can be a troublesome weed.

  • Silver leaf on plum. Image: RHS, Horticultural Science

    Silver leaf

    Silver leaf is a fungal disease of the wood and leaves of some trees, especially plums, apples, apricots and cherries. The fungus infects the wood through wounds and causes a silvering of the leaves followed by death of the branch.

  • © RHS Science

    Sirococcus blight

    This recently recognised fungal disease affects cedars and hemlocks. It causes shoot tip dieback and defoliation. Young trees may be killed if branches/trunk are girdled but it is reported that infected mature trees can live for many years.

  • Slime mould on a lawn. Image: RHS, Horticultural Science

    Slime moulds on lawns

    Slime moulds occasionally cause concern when they appear on lawns, but they do not attack or kill the grass. They vary greatly in their colour, size and form. Their spore-producing structures are often very fragile, disintegrating when touched.

  • Smuts


    Whilst they are not seen as commonly as their close relatives the rusts, smut fungi can affect a range of garden plants, including some widely-grown vegetables and ornamentals. Some smuts cause conspicuous growth distortions, whilst others cause leaf spotting. All can contaminate the soil for extended periods of time.

  • Grey mould on snowdrops. Image: RHS, Horticultural Science

    Snowdrop grey mould

    Grey mould in snowdrops is an infection or disease caused by the fungus Botrytis galanthina, causing leaves and flowers to collapse. A fuzzy grey mould forms under wet conditions.

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