Which diseases can affect Olive trees?
Common olive tree diseases in the UK and how to treat them
Olive trees bring a touch of the Mediterranean to UK gardens, but our damp, mild climate can expose them to various diseases. Knowing what to look out for and how to act helps keep your olive trees healthy, thriving and fruitful. This guide outlines five of the most common olive tree diseases in the UK, with practical tips to identify and manage them.
1. Olive leaf spot
Also known as peacock spot, this fungal disease causes dark, circular patches on leaves. Infected trees may drop leaves early, reducing vitality and fruit yield. It thrives in wet, cool conditions that are common in the UK.
Symptoms: Black or brown spots on foliage, leaf drop.
Prevention: Improve air circulation, avoid overhead watering.
Treatment: Remove heavily infected leaves. Apply a copper-based fungicide such as copper hydroxide during the growing season.
2. Olive knot
This bacterial infection is caused by Pseudomonas syringae. It leads to galls or knots on branches and twigs, which can interfere with sap flow and weaken the tree over time.
Symptoms: Warty, swollen growths on stems and branches.
Prevention: Avoid pruning during wet conditions, disinfect tools.
Treatment: Prune infected branches and dispose of them. Apply copper spray during dormancy to limit bacterial spread.
3. Verticillium wilt
A serious soil-borne fungal disease that blocks water movement within the tree. It’s difficult to eradicate once present, so prevention is key.
Symptoms: Wilting, yellowing or dieback of branches, often on one side.
Prevention: Use disease-free stock, sterilise tools, and rotate crops.
Treatment: Prune affected branches and care for the tree to prolong life, though infected trees often decline over time.
4. Phytophthora root and crown rot
This fungal disease is commonly found in waterlogged or poorly drained soils. It affects the roots first and then spreads to the trunk base, eventually killing the tree.
Symptoms: Wilting, root decay, trunk collar rot.
Prevention: Ensure excellent drainage and avoid overwatering.
Treatment: Remove severely affected trees. Improve soil conditions for healthier trees.
5. Olive anthracnose
A fungal disease that affects the fruit and foliage, especially after warm, wet conditions. Left untreated, it can ruin a harvest.
Symptoms: Dark sunken spots on fruit, blackened leaves, fruit rot.
Prevention: Prune to improve airflow and maintain orchard cleanliness.
Treatment: Apply copper hydroxide. Avoid over-fertilisation, which may exacerbate the disease.
Best advice for nurturing an Olive tree
With care and preventative action, you can maintain healthy olive trees in the UK. Choose a sunny, sheltered position, ensure good drainage, and be vigilant with pruning and hygiene. Sterilise garden tools, avoid overwatering, and feed your olive trees with appropriate nutrients. These simple practices can make all the difference between struggling trees and fruitful success.
About our olive trees
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