Olive Tree Diseases: Peacock Spot, Olive Knot, Verticillium and More

The most common olive diseases are fungal and bacterial problems that thrive in wet weather, dense crowns and wet roots. In gardens, the usual culprits are peacock spot (leaf spots and leaf drop), olive knot (galls on branches) and root rot from poor drainage. Most can be prevented with good drainage, an open crown and a copper spray at the right time.

Peacock Spot (Olive Leaf Spot)

Symptoms: round, dark brown to sooty spots, often with a yellow halo, on the upper side of leaves; heavy leaf drop in late winter and spring, leaving bare shoots.

Cause: the fungus Venturia oleaginea (Spilocaea oleaginea), spread in mild, wet weather.

Treatment: copper-based spray in autumn before the rains and again in late winter; prune to improve airflow; collect fallen leaves.

Olive Knot

Symptoms: rough, corky galls (knots) on twigs and branches; branches beyond the knots may die.

Cause: the bacterium Pseudomonas savastanoi, which enters through wounds from pruning, hail, frost or leaf scars during wet weather.

Treatment: cut out knotted branches in dry weather, disinfect tools between cuts, and apply copper after pruning, frost or hail.

Verticillium Wilt

Symptoms: sudden wilting and browning of one or more branches in spring or summer, with dead leaves staying attached; brown streaks in the wood.

Cause: a soil-borne fungus (Verticillium dahliae), common where cotton, tomatoes or potatoes were grown.

Treatment: no cure. Remove affected branches, avoid over-watering and excess nitrogen, and do not plant olives after susceptible crops.

Anthracnose (Fruit Rot)

Sunken brown spots on ripening fruit, then shrivelled, mummified olives and poor, acidic oil. Common in wet autumns. Harvest early, and use copper sprays before autumn rains.

Root Rot

Caused by Phytophthora and other fungi in waterlogged soil. Leaves yellow and drop, growth stops and the tree declines. The cure is drainage: plant on a mound, never let pots sit in water.

Xylella fastidiosa

A bacterial disease spread by spittlebugs that has killed millions of olive trees in Puglia (southern Italy) and is present in parts of Spain, France and other regions. Leaves scorch from the tips and branches die back until the tree dies. There is no cure; affected areas follow official containment rules. Report suspected cases to your local plant health authority.

Why Are My Olive Tree's Leaves Turning Yellow?

• Overwatering or poor drainage (the most common cause).
• Natural shedding: olives replace some 2–3-year-old leaves every spring.
• Nitrogen deficiency: pale older leaves.
• Peacock spot: yellow leaves with dark spots.
• Too little light indoors.

More Olive Tree Guides

• How to Grow Olive Trees: The Complete Guide
• Why an olive tree isn't fruiting
• When to harvest and cure olives
• How to make olive oil at home

Frequently Asked Questions

What does peacock spot look like?

Round dark spots, sometimes ringed with yellow, on the upper leaf surface, followed by leaf drop.

When should I spray copper on an olive tree?

In autumn before the rainy season and in late winter; also after pruning, frost or hail in wet weather.

Why is my olive tree dropping leaves?

Overwatering, sudden temperature or light changes, frost, drought stress or peacock spot are the usual causes.

Can an olive tree recover from disease?

Peacock spot and olive knot can be managed well; verticillium and Xylella have no cure.