Olive oil production is one of the cornerstones of the agricultural industry in many parts of the world, providing both economic and cultural benefits. However, this invaluable source of liquid gold is threatened by a troublesome pest that was once secondary but is creating more headaches every day: the olive tree borer (Phloeotribus scarabaeoides).
Although the olive tree is a tree perfectly adapted to the Mediterranean climate and considered very hardy, the number of pests and diseases that affect this crop is increasing. However, the olive tree moth is not a new pest, since it has been with us for many years and is gaining momentum with the banning of certain active ingredients in Europe.
For this reason, we consider it essential to know the symptoms of this historical scourge of the olive tree in order to act in the fastest and most energetic way, but always respecting the legislation on the products authorized for this culture. In this article we tell you the main problems related to the borer in the olive grove.
Contents
Characteristics of the olive tree borer
The olive tree borer, known scientifically as (Phloeotribus scarabaeoides), is a Curculionidae beetle, Scolytinae, which can affect Spanish olive trees and which is becoming increasingly important after the ban on the famous dimethoate.
In last weeks of winter When the borers come out of their shelters, they perceive the smell of weak wood, either the remains of pruning carried out at the same time, or slightly weakened olive trees. As its name suggests, this pest works by creating small galleries on the olive wood, slowly weakening the tree.
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Olive branch touched by Phloeotribus scarabaeoides. Photography: Anas A. Emaddescription of the insect
In the life cycle of the olive tree borer, we can distinguish the eggs, the larvae and the adult.
Adult: grayish in color and small in size (2-2.5 mm in length) characterized by several longitudinal stripes, the thorax is dotted and with many short hairs.
Larvae: light yellow in color, with a brown head and a size of 3 mm in length.
Eggs: whitish in color, 0.75 mm long, soft to the touch and oval in shape.
Biological cycle
The adult shelters from winter in galleries previously dug in small branches, unharvested fruits or small leaf inserts. When temperatures rise at the end of winter, the adults move to the olive branches. This mainly coincides with the pruning that is carried out on the olive tree to prepare for germination.
In these galleries, the female lays eggs, hatching larvae that feed on the wood. These galleries are smaller but perpendicular to the galleries dug by the adults (secondary galleries). When the larvae become adults, they dig exit galleries and move towards other olive trees to continue the process.
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When does it act on the olive grove?
In spring, adults of the olive tree borer begin their activity by producing galleries, mainly on the young branches of weakened trees, although they also act on broken branches or trunks, laying eggs in the dug galleries. Borer larvae that form from hatching eggs also excavate their own galleries.
Once the larvae become adults, they leave their galleries and come to the surface in search of other olive trees in the region for shelter from winter until the following spring, when the cycle begins again. Since the borer also takes refuge in pruned wood, pruning management (chipping or burning) is very important, because if it is saved for firewood, the process can be repeated and spread the infestation. If it is kept for wood, it is important that it is done in a well-closed warehouse with no outlets.
Preferences: the pest acts mainly on young wood of medium caliber, especially those located in shaded areas and in a state of average humidity (without excessive movement of sap or completely dry wood). It more easily attacks weakened olive trees and dry areas.
Damage caused by the olive tree borer
The olive tree borer has always been characterized as a secondary pest because the damage it produces is usually light, slowly weakening the tree but rarely causing its death. It is easy to identify by the galleries it creates. If these galleries are very numerous or are in critical branches for the tree, they can in the most extreme cases cause the drying out of entire branches (cancellation of sap flow), resulting in a considerable loss of production.
In the most extreme cases, it can be confused with diseases that cause the tree to dry out completely, such as verticillium wilt, but it is easily distinguished because this disease does not cause holes in the branches. And, as we commented, these holes are extremely easy to identify.
Main damage: weakening of the tree, fruit drop and drying out of entire branches. This may result in production losses of a slight nature. Generally, if more than 3 punctures per branch are observed, the incidence of the pest is high and action is recommended.
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Borer treatments and control
Management and prevention
The prevention of the olive tree borer is extremely important, because once it is inside the branches, in its galleries, it is difficult to carry out chemical control treatments and it is necessary to find the optimal moment for the TO DO.
At the level of prevention, it is very important to manage the size well, because it is the means of propagation of this pest. The earlier the pruning is carried out, the better, since we anticipate the laying of the eggs of the olive tree borer. If, for climatic reasons, it is carried out on the laying dates, it is important to manage the pruning by grinding (organic compost for the soil) or by burning, the first option being more respectful of the environment.
It is important to anticipate the size so that does not coincide with spawning and get rid of pruning debris. If the pruning coincides with the time of egg laying, it is advisable to keep or bury firewood so that insects cannot leave the storage place.
chemical control
In cases where, due to major causes, we observe a level of infestation that requires us to act, although currently there are not many active ingredients allowed (mainly because the olive tree borer has always been considered a secondary pest), we can find effective products if we know the ideal time to apply them.
The ideal moment is when the adult leaves the branches to look for new olive trees to start the cycle. In Spain, it usually coincides with the March and April.
Products to control the olive tree borer
Consultation carried out through the database of the Register of Phytosanitary Products, Ministry of Agriculture of Spain.
| TRADE NAME | MAKER | FORMULA |
| BOLD | FMC Agricultural Soil | DELTAMETHRIN 2.5% [EC] S/S |
| DECIDE | BAIER | DELTAMETHRIN 2.5% [EC] S/S |
| EC DELTA | ELEVATION (P) | DELTAMETHRIN 2.5% [EC] S/S |
| DELTAGRI | ARYSTA LIFE SCIENCES | DELTAMETHRIN 2.5% [EC] S/S |
| DELTAPLAN | BAIER | DELTAMETHRIN 2.5% [EC] S/S |
| ITAKA | FMC Agricultural Soil | DELTAMETHRIN 2.5% [EC] S/S |
| RITME | PROBLEM | DELTAMETHRIN 2.5% [EC] S/S |
| SCATTO | PROTECTION OF GOWAN CROPS | DELTAMETHRIN 2.5% [EC] S/S |
| SUPERDELTA | CHARDA SPAIN | DELTAMETHRIN 2.5% [EC] S/S |
It is important to first consult the authorized active ingredients in an up-to-date manner, as these undergo significant variations over the years.
Biological control
Although not fully defined, more and more sustainable strategies are being sought. Some organisms help to control the borer, the most important being the group of Pteromalids.
- Pteromalids
- Eurytomidae
- Bethylidae
- Braconidae
Related articles on the olive grove
Cover image: gd.eppo.int