Olive leaf spot

Olive leaf spot, also known as peacock spot, is a prevalent fungal disease caused by the pathogen Cycloconium oleaginum (syn. Spilocaea oleaginea). It primarily impacts the foliage of olive trees, impairing photosynthesis and weakening the overall vitality of the plant by affecting the leaf surface.

The primary host for this fungus is the common olive tree (Olea europaea). The disease affects commercial orchards and ornamental olive trees worldwide, leading to premature leaf drop, reduced fruit set, and significant economic losses if the infection remains unchecked over several growing seasons.

The characteristic symptoms include dark-colored, circular spots on the upper side of the leaves. These spots are often surrounded by a yellow halo, creating a visual effect resembling the eyes on a peacock's tail. As the disease progresses, heavily infected leaves turn yellow and eventually fall, leaving branches sparsely covered.

The development of the fungus is highly dependent on environmental conditions, specifically high humidity and moderate temperatures between 15°C and 20°C. The disease spreads rapidly during rainy seasons, as spores are dispersed by water splashes and wind currents within the canopy of the tree.

Effective management strategies combine cultural practices and chemical control:

• Pruning the canopy regularly to improve air circulation and sunlight penetration.
• Removing and destroying infected fallen leaves to reduce the source of inoculum.
• Applying copper-based fungicides as a preventative measure during spring and autumn.
• Monitoring orchard health and selecting resistant olive cultivars for new plantings.