Advice
RHS Help & Advice
Fireblight (Erwinia amylovora)
Plants affected
Only apple relatives including ornamental and edible apples and pears, cotoneasters, Crataegus (thorns), Pyracantha and Sorbus aria (whitebeams). Less susceptible plants include quince, Photinia davidiana and Sorbus aucuparia (mountain ashes). Stone fruits (plums, peaches and cherries) are not affected by fireblight.
Symptoms
Flower clusters wilt and turn black. The foliage looks blackened and scorched, and die back occurs. In spring and summer during humid weather a white ooze may exude from infected wood. Another check is to peel back the bark to see whether the tissues below are stained a reddish-brown colour, initially with a diffuse margin between diseased and healthy tissue.
Cause
Fireblight is a bacterial disease, infecting the plant through injuries or natural entry points such as flowers. From these points, the bacteria spread backwards along twigs, branches and stems. The bacteria are spread by wind-blown rain and insects. Infected branches are killed quickly and a tree can die into two or three years unless prompt action is taken.
Non-chemical control
Prune out infected areas. Infected wood is stained below the bark. You need to cut back into healthy wood well below the last sign of staining, 30cm (12in) in smaller (less than 25mm (1in) diameter) branches and 60cm (2ft) in larger ones. Wipe pruning tools between cuts with a rag soaked with horticultural disinfectant (Jeyes Fluid) or methylated spirit to prevent spread of the bacteria. It is advisable to dig up and destroy the plant if it is small or the attack severe.
Resistant varieties of some plants are available, e.g. the ‘Saphyr’ range of Pyracantha. Check with suppliers for further details.
Chemical control
None is available.
Note: The Department for Environment, Food and Rural Affairs (DEFRA) no longer has to be notified of cases of fireblight that occur in garden situations in mainland Britain. However, in Northern Ireland, the Republic of Ireland, the Channel Islands and the Isle of Man, the disease is not established and the appropriate authorities must be notified.