What is Fire Blight?
Fire Blight is a contagious disease caused by the spreading of the pathogen Erwinia amylovore, a bacterium affecting certain species. Honeybees and other insects, birds, rain and wind can transmit the bacterium to susceptible plant tissue. Injured tissue is highly susceptible to infection, including punctures and tears caused by plant-sucking or biting insects. Once deposited, the bacterium enters the plant through open stomata and causes blackened, necrotic lesions, which may also ooze a viscous fluid, especially in humid weather. The disease spreads most quickly during hot, wet weather and is dormant in the winter when temperatures drop. Infected plant tissue contains viable bacteria and can return upon warm weather in the following year.
Some varieties within the Rosaceae family
How to Identify Fire Blight
Symptoms may appear on blossoms, fruits, shoots, or branches of an affected tree. All symptoms are above ground and are typically easy to recognize. Symptoms on blossoms result in a dull, grey-green appearance and eventually tissues will shrivel and turn black. The base of the blossom and young fruit show similar symptoms as infection spreads. Shoots can show similar symptoms but develop much more rapidly. A “Shepherd’s Crook” can be seen when the tip of the shoot wilts, and diseased shoot leaves typically have blackening along the mid-vein and then die. Initial infection of blossoms and shoots can spread to larger tree limbs. Branches will darken and become water soaked. Advanced infection develops cracks in bark and a sunken surface. Wood under the bark will become streaked with black discolouration. Immature fruit forms water-soaked lesions and later turned black. Bacterial ooze can be found on these lesions. Severe infections result in fruit turning entirely black and shrivelling.
How to Manage Fire Blight
Prune Out the Diseased Wood
All infected branches must be pruned out of the tree at least one foot from the infection site. To prevent the spread of further infection, disinfect the pruners with bleach between each cut. When removing the cut-off branches, be careful not to rub them against healthy branches. Immediately place infected branches into a garbage bag.
Eliminate Infected Branches
Diseased wood must be eliminated immediately, by burning it or putting the sealed bag of infected branches in the garbage.
Monitor regularly to make sure it does not come back. If you spot Fire Blight in your neighbour’s tree, then your tree has a greater chance of becoming infected.