Fireblight (Erwinia amylovora)
What is it?
Fireblight is a bacterial disease caused by Erwinia amylovora. It is a serious disease of apples, pears and other
trees and shrubs in the family Rosaceae.
What are its hosts?
Amelanchier (June Berry)
Chaenomeles (Quince)
Cotoneaster
Crataegus (Hawthorn/Whitethorn)
Cydonia (Quince)
Eriobotrya (Loquat)
Malus (Apple)
Mespilus (Medlar)
Pyracantha (Firethorn)
Pyrus (Pear)
Sorbus (Mountain Ash, Whitebeam)
Photinia davidiana (formerly Stranvaesia davidiana)
History
The disease is native to North America and was introduced to Europe in the 1950s. It has since spread to most
countries in Western Europe. Fireblight was first recorded in Ireland in 1986, but to date the disease has not
become established here. In Ireland, Cotoneaster appears to be the most susceptible host, especially the larger
leaf varieties like C. bullatus, C. Cornubia and C. lacteus.
What are its symptoms?
Fireblight can affect all aerial parts of the host. Primary infection usually occurs in the spring through wounds
in young shoots and through the blossoms. Symptoms vary according to the host but usually include:
 Wilting and death of flower clusters are usually the first symptoms
 Wilting and death of young shoots follows. The dead leaves and blossoms dry up, become dark brown
in colour and usually remain attached to the plant
 Sunken cankers may form and if conditions are favourable the canker can spread along the branch very
rapidly (about 2 inches/day) (the tissue under the bark of cankers is often a reddish-brown colour)
 Fruits and leaves on the infected branches die and turn brown but remain attached to the tree
 In most cases the tip of the shoot bends to form the characteristic ‘shepherds crook’ associated with
Fireblight infection
Life cycle
Fireblight is generally dormant over winter. The bacteria over-winters in living tissue at the margins of cankers.
The disease becomes active again in the spring when temperatures get above 18°C. Rain, heavy dews, and high
humidity favour bacterium growth. Infected tissues exude white bacterial ooze in warm humid conditions and
this ooze can spread infection to other plants when carried by insects, birds, wind and rain.
How does the disease spread?
Fireblight can be spread in the following ways:
 Movement of infected host plants, that may or may not display symptoms, can transmit Fireblight over
long distances
 Rainsplash - Bacteria emerge from infected material in the form of sticky ooze and droplets that harden
on drying but which readily dissolve in water and can be spread by rain splash from an infected host to
adjacent host material
 Wind - Fine strands of ooze may be extruded especially from young tissue and these become brittle on
drying and are dispersed by wind
 Insects can spread the pathogen from over-wintering cankers to early blossoms and between blossoms
Action following discovery of Fireblight
All infected plants must be destroyed under the supervision of the Department of Agriculture and Food. It may
also be necessary to destroy other adjacent host plants in order to control spread of the disease. The source of
the infected material is then traced so that other infected plants may also be destroyed. The plant passport
system facilitates the tracing of Fireblight host plants traded within EU.
What can you do?
Action in the event of suspect cases:
People who have host plants in their nurseries, garden centres and gardens or who have responsibility for parks
and other public areas are requested by the Department of Agriculture to examine their host plants regularly for
signs and symptoms of the disease. If it is suspected that a plant is infected please contact:
The Department of Agriculture and Food
Horticulture and Plant Health Division
Maynooth Business Campus
Maynooth
Co Kildare
01-5053343
01-5053585
The Department of Agriculture and Food
Castle Shopping Centre
Rathbeale Road
Swords
Co Dublin
or alternatively suspect samples may be sent to either of the above addresses. Such samples should consist of
small stems of between 10 and 15cms (4 to 6 inches) taken from the growing tips or from cankered parts of the
plant. Pieces taken from a cankered area should include about an inch of healthy material above or below the
cankered/healthy interface. Samples should be placed in a sealed plastic bag, with details of the host plant,
address where found, and name/contact number.
Leaves showing typical Fireblight symptoms
Shepherd’s Crook, a classic symptom of fireblight
Further symptoms and information on the disease can be viewed on the website of the European and
Mediterranean Plant Protection Organization (EPPO) by clicking on the following links:
Symptoms
Data sheet