La olive harvest, both mechanics and manual, causes wounds and micro-wounds to the plants and, through these, there is the possibility that fungal and bacterial pathogens penetrate, particularly thePeacock eye. The autumnal weather conditions with mild temperatures and high humidity are accomplices.
Peacock Eye Spreading Factors
The Peacock Eye (Spilocaea oleaginea) is a highly moisture-sensitive pathogen, its infections occur when 7-8 hours of leaf wetness accumulate, with relative humidity above 80-90%Fall infections generally have a shorter incubation period than spring infections, but both can cause severe defoliation if not treated promptly.
The yellow circular spots, typical of the infection, expand on the mature leaves, reducing the photosynthetic capacity of the plant and, consequently, its productivity.
Early diagnosis of Peacock Eye
To detect the presence of Peacock Spot early, you can use the method “Loprieno-Tenerini”. This involves immersing the leaves in a 5% solution of sodium or potassium hydroxide. Spots, if present, emerge visibly within 3-4 minutes. However, the method has some limitations, especially in the early stages of infection, where it may give false negatives due to insufficient concentration of pathogens or unfavorable environmental conditions.
Natural defenses of the olive tree
The natural defenses of the olive tree against fungal pathogens are a set of physical, biochemical and genetic mechanisms that allow the plant to counteract their attack. Among the most important compounds involved in these defenses we find theoleuropein, a phenolic compound, present in abundance in the tissues of the olive tree, leaves, olives and bark.
When the plant suffers damage, oleuropein, which has an antimicrobial action, limits the fungi from penetrating deep into the leaves, protecting the internal tissues.
In addition to oleuropein, the olive tree has physical defenses consisting mainly of the leaf cell wall and cuticular tissues. These layers act as a first barrier against the intrusion of fungal pathogens. In Peacock Spot infections, oleuropein not only protects the leaves from direct attack by the fungus, but also reduces its ability to spread, keeping it confined to the surface of the leaves and reducing the impact on the photosynthetic capacity of the plant.
Other fungal pathogens
In addition to Peacock eye, other fungal pathogens affecting the olive tree are: Plumbing, reduces photosynthesis, the Foma, causes lesions on the branches that can lead to the death of the plant, the Botryospheraceae, attack the branches and the trunk, reducing the productivity of the olive grove.
Preventive treatments
After the olive harvest, a phytosanitary treatment with cupric products to prevent the spread of fungal pathogens such as Peacock Spot. Copper acts by creating a protective chemical barrier that hinders the germination of conidia, the propagation structures of the fungus, thus preventing infection of the leaves. The addition of wood distillates and zinc can enhance the effectiveness of the treatment.
It is true that copper has a preventive effect, but it is necessary to be careful of potential phytotoxic effects, especially in conditions of low temperatures or high humidity. In these cases, copper can cause damage to plant tissues, such as leaf burn or defoliation on sensitive varieties.
For this reason, the treatment must be applied when the climatic conditions are favorable, avoiding periods of strong stress for the plant or adverse weather conditions. In conclusion, copper is an effective preventive antifungal, but its use requires correct management in terms of choosing the right time and environmental conditions.
Spring fungicide treatments
In spring, it will then be essential to monitor the evolution of infections and apply preventive or curative treatments based on products such as Dodina, which stops the growth of fungi without causing leaf fall. Products such as Syllit, based on Dodine, are effective if applied at a dose of 800-1000 ml per hectare.
Alternatively, the Strobilurins (for example, Trifloxystrobin e Pyraclostrobin) offer both preventive and curative action, penetrating the leaf tissues. Products such as Flint max (Trifloxystrobin) or Olive Cabrio (Pyraclostrobin) can be used at doses of 300-400 g/ha and 250-300 ml/ha respectively, ensuring long-lasting protection. tebuconazole, in combination with the Strobilurins, further enhances protection against fungal pathogens, including Peacock Spot.
Biological defense products
For those who prefer organic solutions, the Potassium bicarbonate andOrange essential oil are valid alternatives. Bicarbonate alters the pH of the leaf surface, creating an inhospitable environment for fungi. Orange essential oil, rich in limonene, dehydrates and destroys the cell walls of fungal pathogens.
Il Bacillus subtilis It is another natural antagonist that prevents the germination of fungal spores and creates a protective barrier on the plant, limiting the spread of the infection.
Conclusions
Post-harvest disinfection is an essential practice to preserve the health of olive groves and ensure quality production in the following season. Peacock spot control requires an integrated approach, based on the use of chemical and biological treatments, together with careful agronomic management of environmental conditions. Keeping pathogen inoculum low through timely application of fungicides, combined with adequate natural defense, is the key to a healthy and productive olive grove.
AIPO Director
Interregional Association
Olive producers
