English name: Olive Knot Disease
The scientific name: Pseudomonas savastanoi pv. savastanoi
The type of disease: Bacterial disease
Species: Pseudomonadaceae
Symptoms
Olive knot disease is characterized by the formation of tumors or knots on the branches, twigs and trunk of the olive tree.
These nodules can vary in size from small bumps to large, irregularly shaped growths.
They are initially light green or yellow in color and then become darker as they age.
The knots may crack and become rough and woody over time.
In severe cases, knots can surround branches, causing them to die, or to die of the branch or the entire tree.
The bacteria Pseudomonas savastanoi pv. savastanoi
the reasons
This disease is caused by the bacteria Pseudomonas savastanoi pv. savastanoi.
Bacteria enter the plant through natural openings or wounds and colonize the plant tissue, causing the formation of the characteristic nodules.
Propagation conditions
- Olive knot disease can be spread by various means, including:
- Infected reproductive material (such as cuttings or grafts).
- Pruning tools contaminated with bacteria.
- Wind or rainwater carries bacteria from infected plants to healthy ones.
- Insect vectors such as olive fruit flies and olive bark beetles.
- Conditions favoring the spread of the disease include:
- Warm and humid weather.
- The presence of wounds or injuries on the plant.
Losses
- Olive knot disease can cause significant economic losses in olive production.
- Nodules or tumors can reduce a tree's productivity and yield, as well as harm the tree's overall health and strength.
- In severe cases, the disease can lead to the death of branches or even the entire tree.
Control strategy
- Controlling olive knot disease includes a set of agricultural practices, such as:
- Prune and remove infected branches and nodes.
- Proper disposal of striped materials.
- Avoid causing unnecessary wounds to trees.
- Copper-based bactericides can be used for chemical control, but timing and thorough coverage are critical.
Preventive measures
- Preventive measures include:
- Use disease-free reproductive materials.
- Sterilize pruning tools.
- Avoid spraying over treetops, which can promote the spread of bacteria.
- Promoting good ventilation and penetration of sunlight into olive groves.
- Maintain plant strength through proper fertilization and irrigation.
Organic/chemical control of olive knot disease:
Organic control
- Copper-based fungicides or bacteria:
- Copper hydroxide or copper oxychloride can be used as preventive or curative treatments.
- These copper compounds have antimicrobial properties and can help suppress bacterial growth.
- Note: Care should be taken to avoid overuse of copper-based products, as they can accumulate in the soil and cause toxicity to plants.
Chemical control (in conventional agriculture)
- Systemic antibiotics or bactericides:
- They may be used, but their use is often restricted or banned in many countries due to concerns about antibiotic resistance and environmental impacts.
- Examples: kasugamycin, oxolinic acid, eptomycine ester.
- Note: Requires careful application and monitoring.
Possible organic control methods are under investigation
- Vital factors:
- Antibacterial.
- Bacteriophages (viruses that target and kill specific bacteria).
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