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The incidence of the different diseases and pests of the olive tree that can arise in an olive grove or even in a single individual, depends on the following factors:
1. Incidence according to VARIETIES
We are going to see the most common pests that can appear in two of the most common varieties of olives with the most current projection.
- The picual variety is sensitive to verticillosis, and to repilos.
- It is affected by leprosy only in very cold places and with aggressive harvests.
- The picual variety is relatively resistant to flies, tuberculosis and anthracnose.
- The most common pests and diseases in the Arbequina olive grove would be tuberculosis and leprosy.
- The Arbequina variety is relatively resistant to flies and verticillosis and moderately resistant to the repilo.
2. Incidence according to MICROCLIMATES
VALLEYS AND TROUGHS
In a valley, there are large differences in temperature between day and night, and between summer and winter. Temperatures can be extremely high in the central hours of the summer day, and very low with persistent frosts on winter nights. Similarly, the relative humidity is usually very high.
Low zone, with the first frosts, in the month of October.
The main reason for the appearance of these diseased is due to the fact that for many hours a year, the olive trees appear wet and with high temperatures, at the same time that there may be great frosts that make micro-wounds on leaves and branches by which they infect some of the these illnesses.
SAWS, HILLS, PLATFORMS
Olive grove in the mountains. ESAO Image Bank
There tend to be frequent breezes that make the temperatures neither cold nor hot, nor that the relative humidity is high.
They are usually the best locations for the olive grove.
Pests in this type of olive grove in the highlands are rare.
The great mass of water that the seas and oceans represent, print a peculiar climate in the olive groves of the coastal areas. There are no big jumps in temperature between day and night, or between summer and winter. Similarly, the relative humidity is usually high. These conditions are ideal for pest insects, such as the olive fly, the mealybug or the prays.
The incidence of fungi and bacteria is also usually high, due to the high relative humidity and moderate average temperatures.
In coastal areas there is hardly any natural mortality of the olive fly, so the populations and damage are usually very high.
Olive fly. ESAO Image Bank
3. Incidence according to MACROCLIMATESS
HIGH MOUNTAIN AREAS OR NORTH OF CROP DISTRIBUTION
Winter temperatures are very cold, and summer temperatures are mild. Relative humidity depends on the rainfall in the area and its distribution throughout the year. In olive groves in cold and dry areas, the incidence of pests and diseases is usually minimal. In olive groves in cold and humid areas, except in winter, in the rest of the year the conditions are conducive to insects, fungi and bacteria. The pests that could appear in olive groves in these areas are mainly: fly, prays and repilo.
Olive tree very affected by leprosy, due among other causes, to being in a very cold area with strong frosts.
In olive groves located in areas with very cold winters, the incidence of tuberculosis and leprosy is usually high due to injuries to the bark caused by frost.
Olive tree to the north of the natural area of distribution of olive cultivation, very affected by a snowfall and subsequent sub-zero temperatures in the following days.
ZONES OF LOW LEVEL ABOVE SEA LEVEL OR SOUTH OF THE AREA OF DISTRIBUTION OF OLIVE CULTIVATION: WARM ZONES
In areas with hot and dry summers, the incidence of pests and diseases decreases, depending on the wet season. Hot, dry summers have little incidence of flies, prays, or mealybugs. If the winters are humid, it can affect the repilo a lot, although not so much tuberculosis, anthracnose or leprosy.
Dehydrated fruits in mid-summer as a result of high temperatures and the absence of rainfall.
Olive tree in midsummer with severe water stress. Although this situation can limit production in a variable way, it reduces the incidence of pests or diseases during the summer months.
Olive grove in an area with high temperatures that exceed 43º
4. Incidence according to the type of SOIL of the olive oil
CLAY SOILS WITH POOR DRAINAGE
The olive tree is very sensitive to excess moisture in the root, so in these conditions, there is usually an incidence of verticilium and phytophthora, even more so in hot weather conditions.
Soils with a lot of natural aeration, which in principle are beneficial to the root of the olive tree.
Olive groves with this type of soil, the pests that may appear are the larvae of Melolontha spp., Which are very difficult to control.
5. Incidence according to OLIVE GROVE MANAGEMENT
Olive tree pruning, fertilization, irrigation and harvesting have a great impact on the incidence of different pests and diseases. Olives with excessively dense crowns are prone to repilo, tuberculosis, leprosy and cochineal, as an atmosphere protected from the sun's rays and with high relative humidity is created.
Olive tree very affected by repilo, due to an excessively dense crown, in an irrigated trough area. The olive trees are glued to each other.
Olives with excess nitrogen fertilization are more sensitive to spider mites, glyphs (margaronia unionalis), and verticilium, among other pests. In the same way, the vegetative growth is excessive and the crowns become dense and opaque, with the same problems as for lack of pruning.
Young olive tree affected by mites, which usually occurs after excessive fertilization with nitrogen.
Olives with excess irrigation, may have more incidence due to root diseases such as verticillium or phytophtora.
The olive plant with excess irrigation is more tender and leafy, and the same problems appear as due to excess nitrogen fertilization and lack of pruning.
Olive tree affected by root fungi (pytophtora or verticillium), due to excess irrigation in a trough area of the farm.
If the collection produces numerous wounds in the young branches, in early collections, it is very easy to have serious problems due to tuberculosis. Aggressive harvests in cold places aggravate leprosy problems. Late harvests, allow fruits infected by leprosy or anthracnose to infect the rest of the crown.
Wounds produced on the branches during harvesting are the entry point for tuberculosis.
Knowing all these factors and casuistry, we can foresee and act accordingly, before serious production losses occur.
As we are seeing, training is undoubtedly one of the main tools to address the management of our olive grove.
Increasing production and achieving maximum health of our olive grove is one of the objectives that you can deepen in the Olive Grove Management module within the ESAO online Master Olive Oil Consultant Certification.