Advice
RHS Help & Advice
Sclerotinia diseases
Plants affected
Many ornamental plants and vegetables especially lupins, delphiniums, helianthus, beans and lettuce. Attacks on woody plants and grasses are rare. A list of susceptible plants is available to RHS members (send a sae to RHS Advisory Service, RHS Garden Wisley, Woking, Surrey GU23 6QB, quoting your membership number).
Symptoms
Plants may wilt suddenly, showing a yellowing of the lower leaves and toppling over at the point of infection, which is often near ground level. Characteristic symptoms are a brown, soft, wet rot with an associated mass of a fluffy white mould which contains large, hard, dark (usually black) bodies, called sclerotia. These sclerotia are a diagnostic feature of the disease and are generally 0.5-1cm in length, but can be larger and have irregular shapes. When hollow-stemmed plants such as lupins are infected, sclerotia frequently form in the stem cavity.
Cause
Sclerotinia sclerotiorum has one of the widest host ranges of any pathogen. The sclerotia of the fungus overwinter in the soil. In spring the sclerotia germinate to produce a small fruiting body called an apothecium. This releases airborne spores which infect susceptible plants, usually through wounds or senescing plant parts, e.g. dying leaves or petals. Sclerotia remain viable in the soil for up to seven years.
A number of more specialised Sclerotinia species, with narrower host ranges, also exist.
Non-chemical control
- Do not compost affected plant material, as the sclerotia are very resilient and are likely to survive the composting process. Instead, destroy by burning, or seal in plastic bags and place in the refuse bin.
- A number of weed species can also be attacked, so ensure that affected areas are kept weed free.
- Avoid growing susceptible plants on infected land for up to eight years
Chemical control
None is available to home gardeners.