Fire blight and its methods of control and control
Hamid Larijani, faculty member of Islamic Azad University, Varamin Branch
Content of this article
- Introduction
- Disease cycle
- Methods of struggle and control
- Conclusion
Introduction
Fire blight with the bacterial agent Erwinia amylovora is one of the most important diseases of fruit trees (apple, pear, etc.). The choice of the name fire for this disease is a description of the condition of trees that, with their blackened branches and leaves, look exactly like a burning tree.
The first symptoms of this disease appear 2-3 weeks after the flowers open, which are burnt and quickly wrinkle and turn blackish brown. The disease then spreads to the young branches and leaves through the peduncle, and the tip of the branch becomes cane-shaped and gradually dries and turns black. Contamination on the leaves is also caused by the veins, and gradually the leaves are burned, dried, and remain attached to the infected branches.
This discoloration of the leaves appears in black pears, light brown apples and apples. Symptoms on the fruit begin at both the tail and the tip of the fruit, and the fruits are first scalded, then browned and crushed, dried and black, and may hang on the tree for a long time. In wet conditions, a viscous milky liquid with bacterial content is observed on the surface of the fruit.
Disease cycle
When the environment is favorable, the bacteria in the cancers that have overwintered since last year multiply rapidly by cell division and produce a creamy, sweet, sticky liquid called Bacterial ooze. Insects, especially bees, transmit the bacterium to fresh flowers, leaves and shoots. This action is intensified by wind and rain. In spring and at favorable temperatures between 18 and 30 degrees Celsius, the time between infection and the onset of the disease is about 5 days. The bacteria multiply in the flowers and move rapidly to the stem, causing tissue death in a short time.
The bacterium travels through the new branches to the thicker branches and the main trunk, where it overwinters by forming a canker to begin the disease cycle the following year. It is noteworthy that just one active canker can produce millions of bacteria and infect the entire garden.
Fighting and control methods:
To manage and prevent fire blight, it is necessary to perform a combination of prevention and control methods.
- Preventive measures
Garden hygiene included; Weed control, removal of branches or even infected trees, collection of excess leaves, twigs and fruits, autumn plowing, winter picking, etc.
– Planting resistant cultivars and observing the appropriate distance (avoid planting sensitive rootstocks such as M106 and Chinese pear)
– Preparing seedlings, cuttings or scion from healthy and safe areas.
Avoid excessive consumption of nitrogen fertilizers that increase vegetative growth and water the branches and increase the susceptibility of trees to this disease.
– Work tools including scissors, knives, saws, etc. should be disinfected with alcohol or Vitex after pruning each tree.
– Considering that bees are the most important cause of transmission of this disease during flowering, they should be avoided in gardens and infected areas.
Avoid excessive watering during flowering.
B- Control measures:
– As soon as the symptoms of the disease are observed immediately in the growing season, the diseased branches should be cut from 15 cm below the site of infection and collected and burned in a bag.
– Chemical control
– Late autumn with a combination of Bordo 10 per thousand after 70% of leaves fall. Late winter (before bud swelling) with Bordeaux (10 per thousand) or with copper oxychloride (3 per thousand).
– In spring, when the trees are flowering, once when 5% of the flowers are open, once when 100% of the flowers are open, spray with copper oxychloride at a rate of 2 per thousand.
– If you observe the first signs of the disease, spraying with fossil aluminum (elite) in a ratio of 2.5 per thousand.