Which Diseases Affect Olive Trees?

Are you a gardener and you have olive trees to care for? If so, you may know how important it is to maintain healthy trees, but what happens when your olives start showing signs of disease? In the UK, the Mediterranean climate may promote the growth of olive trees, but it also makes them susceptible to diseases. Therefore, understanding what can affect your trees and how to treat them can help produce a healthier crop. This comprehensive guide will detail common diseases affecting olive trees in the UK and how to suppress its symptoms.


  1. Olive Leaf Spot

Olive leaf spot is a common fungal disease among olive trees in the UK, leading to black or brown spots on the foliage, impacting fruit quality and crop yield. The optimal conditions for the disease to thrive include mild temperatures, high humidity levels, and rain, which is common in the UK. For treatment, you need to spray a fungicide like copper hydroxide or mancozeb throughout the growing season. Ensure you start by removing heavily infected leaves before applying fungicides.

Olive Tree Close Up

  1. Olive Knot

Olive knot is a bacterial disease caused by Pseudomonas syringae. The symptoms include bumpy growths resembling knots on olive trees' branches, trunks, leaves, and fruits. Over time, olive knot can lead to reduced yield and even death of your tree. To address it, you can prune affected branches but make sure to sterilise your tools afterwards. Spraying copper spray during dormancy could help suppress the bacteria.


  1. Verticillium Wilt

Verticillium wilt is a soil-borne fungal disease that affects most plants, including olive trees. It hinders water and nutrient uptake by the roots, leading to dry or dead branches and leaves. You could prevent the disease from spreading by sourcing disease-free plant stock, maintaining ethical practices like crop rotation or sterilising your garden tools. It's difficult to treat Verticillium wilt once it's already spread, but pruning affected branches and providing good care to your tree could help prolong its life.


  1. Phytophthora Root and Crown Rot

Phytophthora root and crown rot are fungal diseases that cause olive trees to wilt and die. It attacks the roots and spreads to the crown, leading to collar rot. The disease thrives in poorly drained soils and can survive in soil for years. Prevention is crucial, and you should always ensure proper soil drainage while avoiding over-irrigation. Also, a healthy olive tree planted in sterilised soil is more resistant to Phytophthora.


  1. Olive Anthracnose

Olive anthracnose is a fungal disease that presents brown or black spots on your tree's leaves and fruit with ulcers on mature fruit. It's common after a humid and rainy growing season, and warm weather favours the disease's progress. Proper orchard sanitation and pruning are essential to control the spread of the disease. To treat it, spray copper hydroxide, and avoid over-fertilising.

Olive Tree Wrap


Maintaining healthy olive trees takes commitment and care. Understanding diseases that affect your trees and how to treat them can help keep your trees healthy and productive. Cleaning garden tools, providing proper drainage, sourcing plant stock, and applying preventive measures are some of the practices that could help you avoid diseases affecting olive trees in the UK. By adhering to healthy orchard management, you will have healthy olive trees with bountiful crops!