Fire Blight
Fire blight is a destructive bacterial disease that affects plants in the rose family, particularly species within the genus Malus (apple and crabapple), Pyrus (pear), and occasionally Cotoneaster, Hawthorn, and Quince. This disease is caused by the bacterium Erwinia amylovora and is known for its ability to rapidly kill entire branches or trees in a matter of weeks.
History and Context
The first recorded outbreak of fire blight occurred in the Hudson Valley of New York in the early 18th century. Since then, it has spread across North America and into parts of Europe, Asia, and New Zealand, often through the trade of infected plant material. The disease was named for the scorched appearance of the affected foliage, which looks as though it has been burned by fire.
Symptoms
- Blossom Blight: Flowers turn brown and die, often becoming water-soaked and slimy.
- Shoot Blight: New shoots wilt, turn dark brown to black, and may bend over in a "shepherd's crook" shape.
- Leaf Blight: Leaves wilt, turn brown, and remain on the tree, giving it a scorched appearance.
- Canker: On branches and trunks, cankers form which are sunken, darkened areas, often with a cracked bark.
- Fruit Blight: Fruits become dark, shriveled, and may remain on the tree, often with bacterial ooze visible during wet conditions.
Disease Cycle
The cycle of fire blight begins when:
- Bacteria overwinter in cankers or infected plant parts.
- In spring, during warm, wet weather, the bacteria multiply and ooze out of the cankers or blossoms.
- Insects, especially bees, carry the bacteria to flowers, initiating new infections.
- The bacteria enter through natural openings or wounds, multiplying and spreading through the plant's vascular system.
- Systemic infection can occur, leading to extensive damage and death of the plant tissues.
Management and Control
- Cultural Practices: Pruning out infected areas during dormancy, avoiding excess nitrogen, and choosing resistant cultivars.
- Chemical Control: Use of antibiotics like streptomycin or copper compounds during bloom to prevent infection.
- Biological Control: Some success has been seen with beneficial bacteria and fungi that can outcompete or inhibit Erwinia amylovora.
- Regulatory Control: Quarantine measures in areas where the disease is not yet established to prevent its spread.
Research and Developments
Current research focuses on:
- Developing resistant plant varieties through breeding or genetic engineering.
- Understanding the mechanisms of bacterial virulence and plant resistance.
- Improving biological control methods.
Sources:
Related Topics