Peacock Spot




(Cycloconium oleaginum or Spilocea oleaginea)

Olives Agencies Information Services


During a summer long past, the casual inspection of a Kalamata tree in a home  garden suggested a shortage of water at the roots of the tree. The shorter than normal distance between one set of buds and the next on the young twigs, showed that for some reason the tree growth had been slow.

The tree showed a poor fruit set which still pointed to a shortage of water, at least in the winter when the trees internal preparation for spring flowering was occurring. However, the owner of the tree insisted that it had received plenty of water throughout the year. Didn't this man understand how much water was enough, or was there another problem? A later inspection started to give some answers.

The tree had almost completely defoliated (lost its leaves) by winter, and in  the spring, brand new healthy leaves were shooting vigorously. Why had an  evergreen olive tree lost its leaves? Fortunately, there were still enough of  the old leaves on the tree and on the ground to answer the question.

It was accurately concluded that the tree had been suffering from attacks by a problem commonly known as Olive Leaf Spot or Peacock Spot (Cycloconium  oleaginum or Spilocea oleaginea). Fungal infection by Peacock Spot had caused the leaves to drop. A drastic reduction in leaves each year meant several  months of reduced photosynthesis which resulted in poor twig growth and poor fruit set. So shortage of water was not the culprit.

Sooty blotches are first seen on the leaves in winter. These blotches develop  into greenish-black circular spots that measure up to 6 mm in diameter. There  may be a faint yellow halo around the spot. The lower branches and south side of the tree will be more susceptible than the upper sections. This is believed to  be due to the fungal spores developing faster in shaded, wet and cool conditions as happens lower on the tree and on the south side away from the sun.

Infection is normally associated with high humidity (eg rainfall) and winter conditions (cool and low light). High temperatures restrict spore germination and growth, making the disease inactive during summer.

One or more large round spots will be seen on a leaf and the spots will  sometimes merge into each other. Most of the infected leaves will fall  prematurely by summer. The small number of diseased leaves that remain on the tree during summer will become crusty and whitish and with the cooling of the weather in autumn, a new crop of spores are produced and spread through the  tree's foliage.

To control the disease, infected trees should be thoroughly sprayed with a copper containing fungicide in late autumn. (IMPORTANT: See "Treatment" below) If the problem is severe, then another application may be needed in early winter. This treatment will often eradicate the problem completely. Your agricultural chemical wholesaler will stock a suitable copper fungicide and  application rates should be carried out according to the label's recommendation.

The following excerpt comes from "Olives - Pest Management Guidelines" (UCPMG  Publication 8, 1994). These guidelines cover most possible olive problems found  in Australia and California and are available free at if you would like a copy. (The information comes from California so all references to places, seasons, months and treatments are Californian).

PATHOGEN: Spilocea oleaginea

SYMPTOMS AND DAMAGE: Sooty blotches on leaves develop into green black  circular spots 0.1 to 0.5 inch (2.5 to 12.5 mm) in diameter. There may be a faint yellow halo around the spot. More lesions develop low in the tree. Leaves fall prematurely and twig death may occur due to defoliation.

COMMENTS ON THE DISEASE: The fungus survives on trees in old leaf lesions that have a white, crusty appearance. The margins of these lesions enlarge in fall (autumn) and a new crop of spores develops there. Infection is  associated with rainfall; most infections occur during the winter. High temperatures restrict spore germination and growth, thus the disease is inactive during the warm, dry summers in California.

WHEN TO TREAT: Apply in late October (late April in Australia) before winter rains begin.

TREATMENT: [Due to the chemical nature of the treatments, Olive Agencies is unable to recommend dosages or chemicals to be used. Please check  with your agricultural department and agricultural chemical supplier as to the suitability to olives, method of application and safety precautions needed for copper based fungal sprays. Californian olive growers use Copper sprays.]