What are the types of copper, when sprays are applied, and which dosages are considered correctCopper sprays on olives remain one of the most important plant protection practices, especially in areas where humidity is high and rainfall is frequent. When applied correctly, copper formulations offer effective protection against serious olive diseases, such as peacock spot, anthracnose (gloesporium), and olive knot, which can cause anything from reduced production to the destruction of the olive grove, even shortly before harvest.
As olive producers in Greece face weather conditions, outbreaks of fungal diseases, and production losses every year, the need for valid agronomic guidance becomes more important than ever. The correct choice of copper, timely application, and full coverage of the foliage are the key to maximum protection.
Why copper sprays on olives are necessary for healthy production
Since the 19th century, copper has been used preventively, with the main aim of avoiding infections by fungi and bacteria, offering olive trees a “protective shield”. It is a safe product, which within certain limits is even allowed in organic farming. In practice, spraying olives with copper creates a protective film over the leaves and fruit, which blocks fungi and bacteria. Without this preventive shielding, olives can become particularly vulnerable to diseases, resulting in a reduction in the quantity and quality of olive oil.
The most common olive diseases we treat with copper formulations are:
Peacock Spot: The insidious disease that reduces production
Peacock spot is an “insidious” disease of the olive tree, which is due to the fungus Spilocaea oleagina and usually goes unnoticed by olive producers. When it infects the tree, it causes spots on its leaves and leads to progressive defoliation. As a result, the olive tree weakens, reduces its photosynthesis, and produces far fewer fruits and, therefore, much lower income for the producer.
Gloeosporium (Anthracnose): The biggest danger of recent years for olives
The outbreak of gloeosporium (anthracnose) has caused huge losses in recent years for Greek olive growers. It is a fungal disease that can infect the fruit even shortly before harvest, causing blackening, rotting, and mummification. Even healthy olives can be lost within a few days in damp conditions, particularly from October to November, i.e., a few days before harvest.
Olive Knot: Olive tumors caused by infection after wounds
The disease of olive knot is essentially the creation of tumors on the branches or even the trunk of the olive tree, due to bacterial infection. Pruning, beating (harvesting), hail, or frost open wounds in the tree, which act as entry gates for pathogens. Copper acts as a strong antibacterial barrier that prevents infection by the pathogen and protects your property.
What are the types of copper for spraying on olives and how to choose the right one
Choosing the correct type of copper is crucial for the success of the sprays. Each formulation has its own behavior, different weight on the foliage, and varies in terms of phytotoxicity. Knowing the appropriate type per season and protection need ensures the best possible performance and health of the olive grove.
Bordeaux mixture: Traditional and strong protection
Bordeaux mixture (a mixture of copper sulfate and lime) creates a durable protective layer on the leaves and fruits, ideal for winter applications and after pruning. It is particularly effective against pathogens, but requires caution: it is not used near flowering, can cause phytotoxicity at high temperatures, and the dosage must be strictly adhered to.
Copper oxychloride: The most common choice
Copper oxychloride combines good duration of action with low cost and stable effectiveness. It is ideal for autumn sprays and is often used together with foliar potassium, while its application near harvest should be avoided.
Copper hydroxide: Mild and friendly to new vegetation
Hydroxide is absorbed quickly and does not weigh down the leaves, making it an ideal choice for spring and periods of tender vegetation. Additionally, it can be combined with boron and zinc in healing-type sprays.
Tribasic copper sulfate: The modern and advanced choice
This type of copper adheres very well to the foliage, leaves fewer residues, and is preferred before harvest. It offers strong protection during periods of high risk for gloeosporium and other fungal diseases.
When should copper spray be applied: the correct seasonality
The success of spraying depends largely on the timing of application. Each season requires a different type of protection:
Autumn spray (September–November)
For the most critical spray of the year, copper oxychloride with a foliar potassium formulation is usually used. With the first rains, fungi are activated, and copper must be applied either after a light rain or shortly before a period of increased humidity. Repetition every 10–20 days is recommended depending on the level of infection.
After harvest (Disinfection spray)
Harvesting leaves micro-injuries on the trees. Spraying with copper hydroxide combined with boron and zinc prevents bacterial infestations and helps in the “healing” of the olive grove, protecting the next production.
Winter application (January–February)
During winter, copper protects trees from bacteria and reduces the risk of infection from wounds resulting from pruning. Bordeaux mixture is often used at this stage.
Spring application (March–April)
New vegetation is particularly vulnerable. Copper hydroxide offers mild but effective protection without the risk of phytotoxicity.
What are the correct copper dosages and how are they calculated
The dosage depends on the type of formulation, the concentration, and the size of the tree:
- Bordeaux mixture: concentration 0.8–1.2%
- Hydroxides and copper oxychlorides: 150–300 gr./100 liters of water
- On average, 2–2.5 liters of solution are needed per mature tree
Effectiveness mainly depends on the complete coverage of the foliage. In dense or large olive groves, a high-pressure sprayer is recommended for good penetration into the interior of the canopy.
What every olive producer should pay attention to
To ensure maximum protection:
- Avoid spraying on days with strong wind
- Do not combine copper with oil
- Avoid acidic or alkaline foliar sprays
- Choose formulations based on the season and the risk of infection
- Observe the waiting period before harvest
- Do not overdose, as copper accumulates in the soil
Guidance from an experienced agronomist is essential, especially during periods of high risk for gloeosporium or peacock spot. With careful application, we protect the olive grove all year round, keeping vegetation healthy and ensuring the quality and quantity of production.
Ensogreen: Specialized plant protection services for olive growers
At Ensogreen, we offer comprehensive plant protection and agronomic support services for olive groves of all sizes. With certified formulations, specialized staff and scientific supervision by an agronomist, we ensure effective, targeted applications that protect the fruit, production, and long-term health of the trees.