• Definition

  The olive fly is an insect pest specific to the olive tree, whose larvae develop in the pulp of the fruit. It causes direct damage to olives intended for consumption and a significant drop in the quality of the oil. Under favourable conditions, the economic losses can be very high.

  Development Lifecycle

  1. 1. Overwintering : the fly spends the winter mainly in the pupa stage in the soil (1 to 10 cm deep). Adults or larvae can also be found in the fruit left on the tree.

     2. Spring : emergence of the first adults from the pupae.

     3. Spring–summer : first captures and flights of adults, but spawning begins in August with the beginning of fruit ripening.

     4. Egg-laying : the female lays her eggs under the epicarp of the fruit.

     5. Larva : it develops in the pulp, digging a gallery that alters the flesh.

     6. Pupation : at the end of its development, the larva leaves the fruit to pupate in the soil.

     Generations per year :

     • Saïss region : 2 to 3 generations/year (often autumn)

     • Haouz region : up to 4 generations/year (2 in autumn, 2 on late varieties)

  Symptoms

  • • Premature fall of olives .

    • Presence of larval galleries in the pulp (hollow or softened fruits).

    • Fruit pricked unsuitable for consumption (olive table).

    • Degraded oil quality : high acidity, rapid oxidation, bad taste.

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  Contributing factors

  • • Mild temperatures (20–30 °C) with sufficient humidity.

    • Presence of susceptible fruit at different stages of ripeness.

    • Late harvest, leaving time for several generations to develop.

    • Non-elimination of olives that have fallen or remained on the tree, promoting winter survival.

Preventive control

• Regular collection of fruit that has fallen to the ground.
• Early harvest to avoid late egg-laying.
• Trapping surveillance (e.g., yellow traps, McPhail, pheromone traps or food attractants).
• Good cultural hygiene and disposal of infested fruit.

Biological control

• Introduction or conservation of natural parasitoids (e.g., Psyttalia concolor).
• Use of entomopathogenic fungi in experimentation.

Chemical control

• Insecticide treatment targeted according to catch thresholds.
• Localized sprays with toxic baits to minimize the impact on auxiliaries.
• Compliance with residue limits for olives intended for oil or table.

Sterile Insect Technique (SIT)

• Complementary strategy tested in some regions, effective in combination with other methods.

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