The olive leaf spot, also known as leaded olive is caused by the fungus ( Pseudocercospora cladosporioides Braun 1993). It affects the vigor of the olive tree by damaging the leaves and causing its premature fall to the ground.
The most accepted name of the fungus causing olive leaf spot is Pseudocercospora cladosporioides. However, publications with the synonyms Mycocentrospora cladosporioides and Cercospora cladosporioides can also be found.
The name repilo receives it because the chlorosis produced by the fungus has some similarity with this disease. The leaden surname is due to the color of the underside of the leaf, cause of the fruiting of the fungus.
Microscopic description of Pseudocercospora cladosporioides
Pseudocercospora cladosporioides has conidiophores (spore producers) flexibly. The conidia or spores are elongated and with between 2 and 5 septa (cell walls). The spores have sclerocial bodies (food reserves) and diplodiforms (of different dimensions or shape).
Symptoms of the presence of olive leaf spot
Leaves: the olive leaf spot produces on the surface of the leaf chlorotic spots (similar to those produced by chlorosis) initially yellow in color but which end up becoming necrotic. On the underside of the sheet, irregular and faint spots of silver or grayish color can be observed. The color of the spots becomes more intense when the fungus produces the spores.
Fruits: when the fungus affects the fruit the quality of the oil is reduced and the value of the table olives is depreciated. Fortunately it is not usual for the fungus to end up infecting the olives.
Lead-free control techniques
The fungus infection can be maintained at acceptable levels by applying cultural measures and chemical treatments.
As with the common olive peacock spot and other fungi such as anthracnose, the leaden repilo (Pseudocercospora cladosporioides) develops best in dense and poorly ventilated olive groves. Increasing planting frames and making a correct clearing pruningwill help in the fight.
The treatments used in the control of the repilo (Spilocaega oleagina) are valid against the leaded olive tree.
With these treatments it is usually enough to Pseudocercospora cladosporioides control. However, in case of serious infections (recovery of abandoned olive groves, sensitive varieties, endemic areas…), it is advisable to perform an additional treatment in May by mixing difeconazole with copper compounds ( copper oxychloride, copper sulfate, cuprous oxide, copper hydroxide).
Some treatments with copper salts are allowed in organic farming.
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