Fireblight
From Allotments4All
- Disease type: Bacterium
- Order: Enterobacteriales
- Scientific name: Erwinia amylovora
- English name: Fireblight
 |
 |
Signs of infestation: No visible signs.
Symptoms of infestation: Severe wilting of leaves, shoots and flowers. Ends of shoots show a ‘shepherd’s crook shape, and a bacterial ooze can be seen issuing from the lenticels. Dark brown, burnt- like patches appear on branches, with wilting leaves. Patches spread to the trunk, other branches become infected and the tree can die within 2-3 months. Sunken cankers appear, and if the bark is removed a reddish-brown stain is seen.
Biology, reproduction and spread, and the relationship of its spread to its biology: This is a parasitic bacterium, which is carried by wind-borne moisture in the air, and visiting insects. It can over-winter in living tissue on certain members of the Rosaceae family, such as Malus spp. Pyrus spp. Crataegus spp. Pyracantha spp. and Sorbus spp. As temperatures rise in spring, and the leaf and flowers buds start to open, warm moist conditions enable the bacteria to multiply and infect blossom and the shoot tips. Alternatively, the bacteria can newly arrive during these springtime conditions. It is able to enter the plant through stomata, lenticels and wounds, and is thought to colonise the stigma of flowers and enter through the nectaries. Once it has infected the plant, it multiplies rapidly. Bacteria reproduce asexually, through binary fission, where a cell wall grows through the centre, then each bacterium cell splits into two, and in favourable conditions, this continues until the host food source is exhausted, and the bacteria die unless another food source becomes available.
Prevention and control treatments and methods.
Physical and cultural: Purchase only certified virus-free plants. Check plants regularly for signs and symptoms of infestation. Prune away any suspected recently infected wood 60cm below the site of infection may stop the spread of the disease. Strict hygiene is essential when pruning, tools must be sterilised after each tree has been pruned, to avoid spreading the disease from tree to tree. Avoid planting susceptible trees in known infected areas, and site apple & pear orchards away from hedgerows containing potential native hosts such as Crataegus spp. and Sorbus spp. Plant cultivars with resistance to the disease. Control insect vectors of the disease where possible, which will mean using specific biological or chemical means that do not affect pollinators and beneficial insects.
Biological and Chemical: None
Legislative: Listed as a quarantine disease in the EC Plant Health Directive and the Plant Health (Great Britain) Order 1993, and must be reported to DEFRA if found on registered growers premises. The Plant Health and Seeds Inspector has the power to visit and remove infected plants.
How the disease affects the health and vitality of the host plant: The disease usually kills the plant.
