Olive Tree Diseases


Olive Tree Diseases

Most olive tree diseases are caused by bacteria, viruses and fungi.

Crown Gal

Crown Gal is caused by the bacterium Agrobacterium tumefaciens and it usually concerns young trees. The most common symptom is tumors (overgrowth) that appear in the roots, just above or below the soil line. Infected trees with many galls will gradually become unable to transfer water and nutrients to the upper parts of the tree. As a result, they slowly become weak and they finally die.  The bacterium can survive for many years in the soil.


Verticillium is a very serious fungal disease, caused by Verticillium dahliae. In a few words, the first symptoms of Verticillium is that the olive leaves start to curl and discolor. The infection then spreads to the other parts of the tree (root system), and after a few years it may result in the death of the tree. The pathogen may live in the soil (as spores) for 20 years or more. Thus, olive tree growers must be very careful when choosing the field where they will plant the young olive trees. They must avoid soils where tomato, potato or other vegetables were previously planted, as these crops are also susceptible to verticillium.

Dacus oleae (Olive fly)

The olive fly (Dacus Oleae) hits mainly the olive trees in the Mediterranean region and can diminish the olive production in a few weeks. Dacus is actually a small fly that can only be fed by olives. The main symptom is dark spots that appear in the flesh of the olive fruit. This is where the hole is made and the eggs are laid. Dacus oleae is a very serious problem for olive farmers, because not only does it destroy completely on average 50-60% of the production, but it also affects the quality of the remaining 40%. The acidity of the olive oil is highly increased and in most cases it cannot be marketed for human consumption. In most countries, hydrolyzed baits are used to prevent the population increase of olive fly.

Other olive tree diseases include Cercospora leaf spot, Peacock spots and Olive anthracnose.

You can enrich this article by leaving a comment or photo of your olive trees disease and plant protection methods.


1. Olive Tree Information

2. Growing Olive Trees

3. Are olive farms profitable?

4. Alternate Bearing in Olive Trees

5. Olive Trees Propagation and Pollination

6. Olive Tree Growing Requirements

7. Olive Tree Soil Requirements

8. Planting Olive Trees

9. Olive Trees Fertilization

10. Olive Tree Irrigation Requirements

11. Olive Tree Pruning

12. Harvesting Olives

13. Olive Tree Diseases

14. Q&As Olives


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