Olive fly

The olive fruit fly (Bactrocera oleae) is the single most important insect pest for the great majority of olive plantations in the world.

Global olive production is around 18 million tonnes, around 10% of which are table olives and the rest grown for olive oil. Europe, particularly in Spain, Greece and Italy, accounts for 80% of the world’s production. In many olive-growing areas in the Mediterranean, the sole agricultural income comes from the olive crop. The olive fly has a serious impact on the local economy. Olive fly infestation, at low levels, makes table olives unmarketable and adversely affects the acidity, and hence quality and value of olive oil.

Current control methods against olive fly rely overwhelmingly on the use of chemical insecticides. The biology of fruit flies, where the female injects her egg directly into the fruit, makes it very difficult to kill the larvae – they are never exposed outside the fruit, so fruit-penetrating toxins must be used.  Several useful insecticides have been, or are being, phased out due to concerns about their negative impact on the environment or human health.  Insecticide-resistance is increasing reducing the effectiveness of the chemicals used. The cost of chemicals is also high. For example, in Greece approximately €35 million is spent annually on control of olive fly to prevent estimated losses to the industry (if no such spend) of €650 million. Some alternative control methods such as pheromone disruption, various lures and traps and the parasitoid Psyttalia concolor have been also used to control olive fly but with generally low efficacy, especially when population density is high.

SIT has been proposed for olive fly control since the 1960s. Early research identified the key challenges and solved many of them. However, some could not be solved with the technology and resources then available, and implementation of the research was abandoned.  Recent advances now make it possible to develop an effective SIT system against olive fly.  These include new wild-type strains for rearing, improvements in diet and rearing methods, a much greater understanding of the nature and importance of the microbiota of the olive fly and improvements to field monitoring. A major obstacle has been the lack of a method to separate the exes and thereby to release only males. This is important to avoid damage from females and to overcome some behavioural issues seen in mixed releases. Oxitec has prototype strains of olive fly available for evaluation in the mass-rearing and the field.

Related Publications

McKemey, A., Alphey, L., Koukidou, M., Kramer, A. (2010) Genetic Improvements to SIT for Fruit Fly Control(2010) RIDL SIT Olivefly IOBC.  Integrated Protection of Olive Crops 53: 11- 16.