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Fire blight at a glance:
Latin name : Erwinia amylovora
Common name : Fire blight
Type : Bacterial disease
Symptoms : Flower wilt, cankers, sticky ooze
Dreaded in orchards where it attacks apple, pear and other fruit trees of the same family, the fire blightcan quickly decimate a plantation if it is not taken care of quickly.
What is fire blight?
As the name suggests, fire blight is caused by bacterium Erwinia amylovora. The disease only affects plants in the Rosaceae family : apple tree, pear tree, cotoneaster, rowan (Sorbus), hawthorn (Crataegus), photinia (Photiniaor Stranvaesia) and burning bush (Pyracantha). Note that it does not seem to attack stone fruits such as plum, cherry, peach and nectarine which are nevertheless classified in the Rosaceae family.
Arriving in France in the 1970s, the disease quickly spread and is the subject of constant surveillance. Certain species of plants, considered too sensitive, are also prohibited from planting in France (decree of August 12, 1994).
Recognize the symptoms
For Wrestleeffectively against fire blight, it is essential to know how to recognize its symptoms :
- Of cankers(bark necrosis) appear on branches and trunk.
- A exudatewhite and slimy oozes as droplets from cankers in humid weather.
- Flowers witherthen dieat the time of flowering.
- Young shoots abortwhen the infection spreads through the inner bark (also called a phloem or bast).
- Leaves, branches, floral bouquetsseem burntand take a reddish-brown tintcharacteristic, which gives its name to the disease.
One of the specificities of fire blight is its speed of progression. A branch can die in just a few days and a tree in a few months.
Spread of disease
Like many fungal or bacterial diseases, hot temperaturesand an humid atmosphereare the ideal conditions for the spread of fire blight. This is when the cankers exude the most, facilitating the spread of the bacteria. Erwinia amylovoravia birds, wind, rain, insects, etc.
The disease is spring active until autumnwith a peak in re-vegetation and especially after flowering where the bacteria take advantage of small wounds left by falling petals. Waist-related wounds are also a gateway for the disease.
Treat fire blight
There is no cure (chemical or otherwise) for fire blight. The only way to fight is to take certain actions that will limit the contagion.
- When the disease is declared, remove infected parts by cutting them:
- Peel the bark to reveal the reddish-brown color; sign of infection.
- From the point of contamination, cut at least 30 cm of healthy wood for small branches and at least 60 cm for larger ones.
- Disinfect your tools between each cut!
- Burnall parts cut.
- Remove cankers. As the bacteria stay there in the winter, they will contaminate your tree again the following spring.
- If a subject is too damaged, tear it off and burn it.
- Remove secondary flowers before they open.
Important : it is essential to burn all plant waste contaminated by fire blight. The disinfection of any tools (and whatever the operation) is also mandatory. Note that even outside the period of infection, it is strongly recommended to do so.