The olive tree is one of the most emblematic and valuable crops of the Mediterranean region, prized both for its fruit—the olive—and for the oil extracted from it. However, its profitability and longevity are constantly threatened by a wide variety of diseases and pests . A thorough understanding of these problems, their symptoms, how to differentiate them, and the most effective treatments is essential to ensure the health and productivity of olive groves.
Main pests and diseases that affect the olive tree
Olive tree diseases and their treatment are fundamental to maintaining the production and quality of olives and olive oil. There are various causal agents, ranging from fungi and bacteria to insects and adverse environmental conditions. Below, we detail each of the most important pests and diseases, their symptoms, their impact on the olive tree, and the most recommended strategies for their prevention and control.
Olive bug
Olive tree borer infestation is caused by the insect Euzophera pinguis , which feeds on the bark and wood of the tree. This gradually weakens both young and adult trees. It is a significant pest, especially in new plantations, although under normal conditions its natural predators help keep its population under control. Symptoms include galleries in the bark, progressive weakening, and reduced productivity.
For treatment , it is advisable to monitor the condition of the trunks, encourage the activity of natural predators, and, in the case of a severe outbreak, use specific insecticides approved for olive cultivation. Pruning and removing affected branches is also an important preventative measure.
Olive mite disease
Olive mite infestation, also known as olive acariosis or erinosis, is caused by microscopic mites of the genus Eriophyes . These tiny arthropods cause severe deformities in leaves and fruit , as well as the appearance of galls and visible webbing on young shoots. The affected plant exhibits a bruised and chlorotic appearance in its foliage, leading to its overall weakening.
Control relies on the use of authorized acaricides and monitoring the phytosanitary status of the plantation, especially after mild winters. It is vital to avoid excessive use of nitrogen fertilizers and to promote biodiversity to encourage the presence of natural enemies.
Soapy olive or anthracnose
Soapy olive disease , or anthracnose, is caused by several fungi of the genus Colletotrichum . This disease is one of the most economically and agronomically damaging, as it can lead to weight loss, premature fruit drop , and a significant reduction in the quality of the oil produced.
Symptoms include the appearance of olives with a moist, soapy appearance and brownish-black spots, mummified fruit, and defoliation. The fungus thrives in humid environments and moderate temperatures, so its incidence varies depending on climatic conditions.
Control emphasizes sanitary management practices (removal of affected fruit, aeration through pruning), the selection of resistant varieties, and the use of specific fungicides before and after prolonged rains.
Olive milkweed
The cottony cushion scale (a psyllid belonging to the family Psyllidae ) is a secondary pest, but when left unchecked it can cause significant damage to the tree's vegetative development. It is easily recognized by the presence of white, cottony masses on the undersides of the leaves, the result of the insect's secretions.
It feeds by sucking sap, which causes weakening, chlorosis, and stunted growth of shoots. Biological control is usually sufficient in most cases, thanks to predators such as Chrysoperla carnea and Anthocoris nemoralis . When necessary, authorized insecticides are used, prioritizing those that preserve beneficial insects.
Root asphyxia of the olive tree
Root asphyxiation is a physiological disorder caused by excess water and poor soil drainage, conditions incompatible with the biology of the olive tree, which requires well-aerated soils for the proper development of its roots.
Symptoms include leaf wilting, premature leaf drop, and root rot . This condition can facilitate the entry of other pathogens such as Phytophthora . To prevent it, it is essential to ensure adequate drainage, avoid excessive watering, and select suitable rootstocks if the soil is prone to waterlogging.
Olive spider mite
The olive mite ( Liothrips oleae ) is a small insect that causes defoliation, fruit deformities, and general weakening. It tends to attack more frequently during mild winters and wet springs. It is distinguished by the spots and deformities it leaves on young shoots and cut shoots.
Control is primarily biological, given the high effectiveness of its natural predators. In severe cases, selective insecticides can be used, always following current regulations.
Olive borer
The bark beetle ( Hylesinus oleiperda ) is a wood-boring insect whose activity increases after pruning and periods of tree weakness. The female lays eggs under the bark, and the larvae excavate galleries, affecting sap flow and weakening the tree.
Prevention is the best strategy : prune outside of the insect's flight period, remove affected wood, and use monitoring traps. If necessary, apply authorized insecticides immediately after pruning and before the spring flight begins.
Ceramide (white worm) from the olive tree
The olive weevil ( Melolontha papposa ) primarily damages the roots, posing a particular threat to young olive trees. The larvae feed underground, which can go unnoticed until the tree exhibits severe symptoms such as wilting and loss of vigor. Control measures include cultural practices such as shallow plowing and the application of insecticides if the infestation is severe.
olive mealybug
The scale insect ( Saissetia oleae ) is a significant pest that sucks sap, weakening the tree. Its honeydew excretions encourage the growth of fungi such as sooty mold, exacerbating the symptoms. Scale insects are difficult to eradicate due to their protective shell.
Control includes the use of mild insecticides such as mineral oils or growth regulators, and encouraging the presence of natural enemies. In severe situations, more intensive products are used, alternating action mechanisms to prevent resistance.
Olive shield
Olive scab (a fungal disease caused by Sphaeropsis dalmatica or Camasporium dalmaticum ) results in necrotic spots, craters on olives, and, in severe cases, mummification of the fruit. The fungus is easily spread by insects, and although it usually has a low incidence, it can affect the marketing of table olives.
Control is achieved with specific fungicides and cultural management (removing infected fruit and pruning affected branches).
Olive tree glyphs
The jasmine moth ( Palpita unionalis ) is a particularly damaging pest in young jasmine crops, as it destroys tender shoots and can seriously delay tree development. It is more dangerous in cool, damp areas.
Prevention consists of visual inspections, formative pruning, and biological control. If the pest thrives, applying specific insecticides is effective, always at the right time in the insect's lifecycle.
Olive leprosy
Olive leprosy is caused by the fungus Phlyctema vagabunda . It produces lesions on the fruit, defoliation, and premature olive drop. It is more common in humid environments and at low temperatures. It affects profitability by reducing the quality and yield of the olives.
The treatment recommends sanitary pruning and copper-based phytosanitary products in the period before rain or when there are early symptoms.
Olive fly
The olive fruit fly ( Bactrocera oleae ) is considered the most destructive pest. The female lays her eggs in the pulp, and the larvae consume the fruit's interior, creating galleries that facilitate fungal entry. Damage includes premature fruit drop, fruit unsuitable for oil or consumption, and significant economic losses. Several generations can occur each year, depending on temperature and humidity.
Management integrates monitoring with traps (pheromones, chromotropic and chemotropic) , selective chemical treatments, early harvesting and favoring resistant varieties.
Black olive
Sooty mold is a fungal disease caused by fungi of the genus Capnodium and related species, which grow on honeydew excreted by sap-sucking insects such as mealybugs and aphids. The most characteristic symptom is a black coating on leaves and branches, which hinders photosynthesis and weakens the tree.
For its control, integrated pest management is recommended to prevent the appearance of honeydew-producing insects, in addition to the application of copper products and the removal of diseased plant material.
Olive Otiorrinco
The otiorhynchus is a beetle whose larvae feed on roots, and the adults on leaves. It can severely limit growth and production, especially in young trees and in compacted soils.
Control measures include maintaining aerated soil, regular inspection, and applying insecticides at key times in the insect's life cycle.
Prays or olive moth
The olive moth ( Prays aureus) develops three generations annually: phyllophagous (leaf-eating), anthophagous (flower-eating), and carpophagous (fruit-eating). The most serious damage is caused by the carpophagous generation, which causes the premature drop of still-green olives.
The management strategy includes monitoring different generations and the use of biological insecticides and traps, along with agricultural practices that minimize incidence.
Repilo or rooster's eye
Olive leaf spot ( caused by Spilocaea oleaginea or Cycloconium oleagineum ) is considered the most serious disease of the olive tree. It causes dark, circular spots on the leaves, severe defoliation, and weakening of the tree. Its severity depends on humidity, temperature, and varietal susceptibility.
Control requires preventative copper treatments before the autumn rains, pruning to improve ventilation, and removing contaminated fallen leaves. Varietal selection is key; some varieties are highly susceptible and others are more resistant.
Olive tree tuberculosis
Tubercle is caused by the bacterium Pseudomonas savastanoi . It manifests as tumors or warts on branches and trunks, sometimes on leaves, after the bacteria enters through wounds or pruning. The tumors grow, crack, and can severely affect production.
Prevention is key: avoid wounds during pruning and disinfect tools. There's no cure, but applying copper-based products after pruning and removing infected branches helps reduce the impact.
Olive tree verticillosis
Verticillium wilt is caused by the fungus Verticillium dahliae . It enters through the roots and blocks the vascular system, resulting in wilting, decline, and partial or total death . Its persistence in the soil makes it one of the most difficult pathogens to eradicate.
Treatments include planting only certified, healthy cultivars, strict residue control, and rotation with non-host crops. The use of resistant varieties and soil solarization can reduce incidence.
Xylella fastidiosa
Xylella fastidiosa is a highly dangerous bacterium for olive trees and other woody species. Its main symptom is wilting, drying of leaves and branches, and eventual death of the tree . It is transmitted by insect vectors and currently has no direct cure.
Control is based on prevention, including phytosanitary surveillance, the use of plant material free of the bacteria, and the immediate elimination of infected specimens, in addition to controlling insect vectors through appropriate phytosanitary treatments.
How to detect olive tree diseases: symptoms and signs
Early detection is one of the best tools for minimizing the impact of diseases and pests. Regular monitoring is essential:
- Leaves: unusual stains, color changes, presence of dust or cottony masses.
- Fruits: deformations, stains, galleries or premature fall.
- Branches and trunks: tumors, cracks, discoloration or abnormal sap flow.
- Roots and base of the trunk: symptoms of root asphyxia, rot or presence of galleries.
Any abnormality in the tree's regular development and the appearance of symptoms should be reported to an agricultural technician or specialist to identify the problem and apply the most appropriate treatment.
Methods for preventing and controlling olive tree diseases and pests
The control and prevention of diseases and pests in olive trees is based on a comprehensive strategy:
- Olive grove hygiene and management: Remove fallen leaves and fruit, prune properly, and keep tools disinfected.
- Irrigation control: avoid waterlogged soils and excessive watering.
- Varietal selection: plant varieties less susceptible to the main diseases of the area.
- Responsible phytosanitary treatments: Use fungicides, insecticides and acaricides, always following the technical recommendations and promoting product rotation to avoid resistance.
- Monitoring and Traps: Use of pheromone, chromotropic and chemotropic traps for insect monitoring and control.
- Promotion of auxiliary fauna: protect and increase the biodiversity of the olive grove, encouraging the presence of natural predators.
- Biologic control: use of specific biological agents to combat pests.
Current advances and recommendations for the protection of olive groves
Innovation in olive phytosanitary management continues to advance, with the adoption of integrated programs that combine:
- Certified seedlings, pathogen-free, from specialized nurseries.
- Biological and plant treatments, especially in soils with a history of verticillium wilt or in areas with high disease pressure.
- Responsible use of phytosanitary products, respecting integrated production protocols and always promoting the lowest possible environmental impact.
- Solarization and biofumigation of the soil in new plantations or in the replacement of trees affected by persistent fungi.
The success and longevity of an olive grove depend largely on the ability to quickly identify any health problems in the trees, implement effective preventive strategies, and apply appropriate treatments according to each situation. Detailed knowledge of the most common diseases and pests, combined with good agricultural practices and the incorporation of the most modern advances, guarantees not only the sustainability of the olive tree, but also the quality and value of the oil produced.
