Greek scientists believe they have discovered a method using genetic engineering that will prevent olive fruit flies from affecting the production of olives and the acidity levels of olive oil, it was revealed yesterday. The flies, known as Bactrocera oleae or Dacus, are the most serious pest to olive trees in the Mediterranean and their habit of laying eggs in olives can cause much damage to harvests. Until now the most common way of protecting olive trees has been spraying them with pesticides, but scientists from the University of Crete and the Technology and Research Institute believe they have come up with a more effective method. The Sterile Insect Technique (SIT) has been used in the past to curb the population of several pests but had proved impossible to apply to Dacus. The technique involves the release of sterile male insects into the atmosphere but it is only with this latest breakthrough that scientists have been able to separate male and female olive fruit flies and sterilize the males.