Olive Tree Diseases: [Characteristics, Types, Detection and Treatment]

What are the diseases of the olive tree and how can we detect them?

The olive plant is susceptible to attack by numerous phytophagous and pathogens, which maintain a fragile balance with their host.

Olive tree diseases cause crop losses that can compromise the productive capacity or the life of the tree.

In recent years it has been found that climatic conditions sometimes favor the development of some olive tree diseases.Among the main diseases of the olive tree are those caused by fungi (mycoses) that affect leaves and olives (especially Repilo, Anthracnose and Emplomado).

Other lesions are caused by root mycoses (Verticulosis and root rot caused by the Phytophthora fungus).Other diseases that attack the olive tree are caused by bacteria, including Tuberculosis or warts and various anomalies due to abiotic factors.

Description of olive diseases

The most prominent diseases that affect olive cultivation are:

Repilo or ocular spot of the olive tree or turkey eye

Produced by the fungus Spilocaea oleagina and is characterized by the presence of dark brown circular spots on the upper surface of the leaves, sometimes surrounded by a yellowish halo.

Leaded or leaded repilo

Fungal-like disease caused by the fungus Pseudocercospora cladosporioides.It is a widespread disease in most olive-growing regions, affecting leaves and fruits, causing serious defoliation, fruit drops and general weakening of the tree.

anthracnose

Also known by the name of soapy or mummified olive and is produced by the fungus Colletotrichum, spp.

It produces the rotting of the olives, weight loss and their fall. The affected olives produce oils of poor quality, with a high acidity index (“colored oils”).

Desiccation and death of branches that supported the infected fruits have also been observed.

Verticulosis or lightning plague

It is a disease caused by the fungus called Verticillium dahliae. When the olive tree has this disease, two symptoms are distinguished called «Apoplexy» rapid death of the branches and the plant and «Slow decay» which is the desiccation and mummification of the inflorescences.

Tuberculosis

It is a disease caused by a bacterium called Pseudomonas savastanoi, which reduces growth and the fruit acquires a bitter, rancid or salty taste that decreases the quality of the oil.

How to identify and eliminate olive tree diseases?

The cultivation of the olive tree is highly valued in the world and because it is an edible fruit of great culinary value, studies and research have been carried out to combat and identify the diseases that attack it:

The Repilo, vivillo” or fall of the leaves of the olive tree

It is the most common disease of olive groves and causes serious defoliation that progressively weakens the tree.

The most characteristic symptom of the disease appears on the upper side of the leaves, where circular spots of variable size and dark brown-black color can be seen, frequently with a yellow halo.

To prevent the disease it is recommended to ventilate the plants, selective pruning and the use of plantation frames that avoid the formation of dense crowns or joints. In terms of chemical control, the most used are copper fungicides, with which the crown, lower branches and plant should be thoroughly wetted s/interior/»>interiors of the plant.

Leaded or leaded repilo

It is one of the olive tree diseases least known by farmers and attacks both the upper and lower sides of the leaves.The name of the disease refers to the grayish coloration that appears on the underside of the leaves, mainly in the oldest ones, due to the pathogen’s conidia.

This disease can be attacked through selective pruning and plantation frames that avoid the formation of very close crowns, creating a less favorable environment for its inoculation.

anthracnose

It is the most relevant disease of the fruit and the most important that affects the olive tree in humid areas where susceptible varieties are grown.Some olive growers know it as a soapy olive, referring to its best-known symptomatology, the soapy-looking rot on the fruit.

It is also recognized because it dries out and causes the death of the branches of the tree.Bringing forward the harvest date is a form of escape that reduces the severity of epidemics.

The chemical control of the disease is based on the use of copper fungicides, ensuring that the crown of the tree is well protected without escape zones.

Verticulosis or lightning plague

It can be detected in two ways: in some cases, diseased plants experience a slow decay, generally accompanied by necrosis in the inflorescences.A second form of expression of the disease corresponds to a rapid death of shoots, main branches and secondary branches.

Although the disease can affect olive plants that are 50 years old or older, it has been proven that the most severe attacks almost always occur in new plantations, with plantations between 5 and 6 years of age being more susceptible.

Control: Like most vascular diseases caused by fungal organisms, olive verticulosis is difficult to control.

Among the factors that make it difficult to control are its wide range of hosts, its ability to survive for a long time in the soil and its location in the xylem, which makes access difficult for chemical treatments.

To combat this disease, the following have been studied: measures before planting: choice of non-infected soils for cultivation; recovery of infected fertile soils; use of inoculum-free planting material; use of tolerant cultivars.

Post planting measures: cultivation practices unfavorable to pathogens; use of organic matter and solarization in adult plants; chemical control although it has been proven that fungicides are not effective against the disease.

Tuberculosis

Affected olive trees have warts, tumors or galls on the branches that cause less vigor of the tree, reduced growth and the fruit acquires a bitter, rancid or salty taste that decreases the quality of the oil.

The best way to combat this disease is the use of cultural practices (removal and burning of diseased parts, disinfection of used tools) Natural products (copper salts) or chemical products.

Bibliography and references

• Trapero Antonio, Juan Moral. Olive diseases. Reproduced from: https://www.researchgate.net/publication/322992304_Enfermedades_del_olivo. (PDF)
• Quiros, Carlos. Erika Gonzalez . Olive orchard management manual. The Agricultural Development Institute (INDAP) and the Agricultural Research Institute (INIA). Santiago de Chile. Reproduced from: https://www.inia.cl/wp-content/uploads/…/16%20Manual%20 Olivos.pdf
• Ortega, G. Teresa. 4 main pests and diseases that affect the olive grove. Reproduced from: https://silo.tips/download/4-principales-plagas-y-enfermedades-que-afectan-al-olivar-41-plagas-principales (PDF)