Treatment of the olive pit
The weevil has always been the most serious problem in olive cultivation and its fight is necessary to have a good and quality production of table olives and olive oil.
The olive borer is an insect that attacks exclusively the fruits of olive trees and wild olives.
It is a type of small fly that causes extensive damage to olives every year.
As olive oil is the most important Greek agricultural product with enormous economic importance, the effective treatment of the disease by olive growers is more than imperative.
To combat the borer, during the summer and autumn, olive growers spray several times with chemical preparations obtained from agricultural stores.
The extensive spraying of olive trees with chemical insecticides to deal with the olive borer, has over time caused a reduction in the beneficial insects of the olive resulting in an increase in attacks by various insects such as the olive cotton.
In today’s article, we will see in detail what damage the olive borer causes to olive trees, which conditions favor its spread and in what ways the biological control of the borer is carried out. .
What damage does dakos cause to olives?
The weevil destroys part of the flesh of the olive fruit and the damage it causes is initially quantitative, as we have an increased rate of fruit drop and reduced production.
In the next phase, the damage caused by the dakos is also qualitative, as the produced olive oil is degraded due to increased acidity.
The intense attack by dako and the creation of wounds in the olives in the autumn period can cause the secondary attack by fungal diseases such as gliosporia, camarosporia and cycloconium, which in environmental conditions causes rotting of the olive fruit and further degradation of the product.
The amount of economic damage caused by the olive borer varies from last year, depending on the extent of the infestation and the effectiveness of its treatment.
In some cases, the economic damage of the daco to the olives and the olive oil produced can exceed 50% of the value of the produced product.
What conditions favor the development of the olive pit?
The dakos grows in cool conditions and relatively low temperatures, when the average daily temperature is lower than 25°C and higher than 10°C.
When the temperature exceeds 35°C for many days, the population of the dako decreases, its activity and also its fertility.
Conditions of high atmospheric humidity and the rain in summer and autumn favor the proliferation and spread of the fungus as well as the increase in its activity.
Olive trees cultivated intensively, i.e. watered, fertilized and pruned, are more susceptible to the disease than olive trees cultivated dry, due to higher humidity and higher production of olive fruit.
How does dakos spread during the year?
The olive borer usually completes 4-5 generations on olive trees during a year. When we say generation of the insect, we mean its life cycle (biological cycle of the insect) which includes the successive stages: egg – larva (caterpillar) – chrysalis – perfect insect (fly).
The generations of the stinging insect appear in specific periods of time each year, depending of course on the prevailing weather conditions as we describe in detail below:
In the spring, the 1st generation of the insect is active, and a gradual appearance of the pit insects is observed.
In early to July the 2nd generation of the weevil occurs, where the females oviposit on young green fruits.
In August and September, the 3rd and 4th generations of the olive pit appear respectively in the development and ripening stage.
In the autumn season, if we have high temperatures, a 5th generation may follow in the final stages of olive fruit maturation.
How are bin populations monitored?
The effective treatment of the daco requires the careful monitoring of the evolution of its population, from the end of spring when it appears to be able to assess when are the appropriate times to intervene.
To monitor the borer on olive trees, we use special McFail-type observation traps or improvised observation traps using plastic water bottles with holes drilled in them.
We hang the observation traps in a cool spot on the north side of the tree.
In any case, to create observation traps, we use a 2%-3% solution of ammonium sulfate or hydrolyzed protein as a bait attractant, i.e. about 2 tablespoons in a liter of water. Ammonia sulfate and hydrolyzed protein can be found in agricultural stores.
How is the biological control of dako?
To combat the dako in organic farming, detailed approved ecological methods, as we describe in detail below:
- We hang traps in olive trees Hanging traps for mass attraction, trapping and killing of the weevil in olive groves is recommended when weevil populations are relatively low as they have limited effectiveness.
The specific olive pit traps carry ammonia, hydrolyzed protein, chemical insecticide and sometimes sex attractant pheromone. The traps must be hung on the north side of the tree, at least one for every two trees, in such a way as to create a barrier preventing the weevil from entering our olive groves.
We do bait spraying of the olive trees
Bait spraying of olive trees is the basic and most economical way of dealing with scab used both in conventional olive cultivation and in organic farming using approved formulations for spraying.
When we notice that the number of weevils has increased in our crop, we can do a bait spray with an approved organic formulation that we get from agricultural stores.
With decoy spraying, we do not spray the whole tree, but spray only a limited surface of the foliage.
In sparsely planted olive groves, bait spraying is done on every tree in the olive grove, while in densely planted olive groves, it is done on every second tree.
Spray an area of one square meter from the north side, using about 300ml of spray solution in the inner shady part of the olive tree.
The number of operations varies according to the area and the size of the population of the dako. For greater efficiency, it is good to perform the operations in groups in each area.
- Spray the olives with kaolin.
Kaolin is a natural mineral, approved for use in organic farming to treat scab by spraying on the foliar surface of the olive tree.
By spraying kaolin on the olive trees, a thin white film is created, which acts as a repellant to the laying of the eggs of the weevil, as well as to its feeding.
Typically, two sprays are required for the best and most effective control of scab during the growing year, one in early summer and one in late summer or early fall.
When spraying with kaolin, an additional adhesive is used for better wetting, while the water should be splashed frequently for better homogeneity of the solution and disinfection of the spray.
- Spray the olives with natural pyrethrum
In conditions of intense infestation by the weevil, the olive trees can be sprayed with natural pyrite, for the biological control of the weevil.
Natural pyrethrum as an ecological insecticide is approved for use in organic farming to deal with various insects in crops.
It is important to remove from our field the olives that have fallen to the ground after the harvest as they are foci of the dako insect and contribute to the more intense infestation of our olives in the following growing year.