Damage of such extent has not been seen in 30 years, Viljanka Vesel of the Nova Gorica Agricultural and Forestry Institute has told the STA, noting that this is due to a combination of several circumstances.

These include high temperatures in the past winter, the early growth on oil trees in the spring, as well as the summer being characterised by low temperatures, frequent raining and high humidity, according to her.

While this year's harvest was originally expected to be a flop compared to past years, the infestation by olive fruit flies is putting an insult to injury, as a lot of olives are falling off the trees too early.

"I think it will be good if we are left with a quarter of the usual harvest," Vesel said, adding that the quality of olive oil could also be affected.

She also noted that another reason for this year's poor harvest is the administrative barriers for the use of specific pesticides that could have prevented or restricted the damage.