• English
  • العربية
  • 中文
  • Français
  • Русский
  • Español

You are here

Nuclear Science Protects Revered Fruit

The Olive Fruit Fly only lays its eggs in olives. It can infest up to 90% of a farmer´s fruit, damaging the crops and the livelihoods of the olive growers and exporters. (Photo: FAO/IAEA)

Homer wrote about olives in his Odyssey, Hippocrates praised olive oil for its medicinal purposes and olive tree leaves were found in the tomb of Tutankhamen.

But despite being revered by kings and symbolising peace, this ancient tree is being attacked by Bactrocera oleae, more commonly known as the olive fruit fly.

This small, innocuous-looking pest, which only lays its eggs in olives, can infest up to 90% of a farmer´s fruit, damaging the crops and the livelihoods of the olive growers and exporters.

The fly poses a serious threat to the olive and olive oil industries in southern Europe, North Africa, the Middle East and the USA.

However, help could be at hand for farmers affected by these olive-eating pests in the form of nuclear technology.

Scientists from the Joint Division of the IAEA and the UN´s Food and Agriculture Organisation are working on a project to control the fly using the proven and environmentally-friendly Sterile Insect Technique (SIT), which uses radiation to sterilise pests.

This technique, also known as "birth control for insects", suppresses populations by breeding large numbers of sterile males. When released into the wild, they breed with females who in turn produce eggs that do not hatch.

FAO/IAEA entomologist, Andrew Jessup, said: "SIT has worked in the past with other fruit flies and it´s now being put to the test to combat the olive fly in southern Israel."

"This current release project in Israel is the first SIT project on the olive fly since the 1970s, when the IAEA was involved with releases in Greece. These early experiments were promising, but didn´t move on because of the difficulty in mass-rearing this insect."

The IAEA´s Laboratories at Seibersdorf, south of Vienna in Austria have been supporting the Israeli olive fly project for several years. Scientists there have bred wild Israeli flies with female flies, and their offspring, in the form of sterilised pupae, were sent to Israel for early experiments in olive orchards.

The current release project, which is coordinated by the Agricultural Research Organisation and the Plant Protection and Inspection Services - branches of the Israeli Ministry of Agriculture - is also supported by the IAEA´s Department of Technical Cooperation.

Israeli entomologist, David Nestel, who is leading the project, said: "The olive fly affects both table olives and olives for oil. With no treatment against this pest, damage can reach 100%."

"Currently, the main control method is spraying pesticides. But if SIT is effective, it´s expected to help control the problem in an integrated fashion with other environmentally-friendly methods."

David Nestel and his team are currently releasing around 40,000 sterile flies a week in an isolated, olive-growing plot in the Lahav Forest in the Negev region of Israel. The project will run until December 2010.

"It´s too early yet to know the effects of sterile fly releases, but from field data we know that the released fly is very robust and is showing good dispersal capabilities," he said.

The sterile flies for mass release are being produced by the Israeli company Bio-fly that was established in 2005 with the support of the IAEA following a successful SIT project to suppress the Mediterranean fruit fly in an Israeli-Jordanian valley.

If the SIT technique is working the population of wild pests should be suppressed, since the females, after mating with the mass-released sterile males, will produce eggs that do not yield offspring.

The success of a project can be assessed by trapping flies in the release areas to see if the sterile flies are outnumbering their wild counterparts.

"The sterile pupae are dyed for identification. With the dye marker we can identify the sterile flies that were released and discern them from the wild flies," said David Nestel.

He added that his team are monitoring the population trends of the flies in the areas where the sterile flies are being released and comparing them with data from reference areas with wild fly populations.

"In addition, we will check and compare the percentage of olive damage and infestation in both the release and reference areas. We expect to be able to evaluate the success of the project in a year from now," said the entomologist.

The olive fly lays only one egg per olive. When the larva hatches it eats the fruit, damaging the olive. A female can lay up to 15 eggs a day, so swarms of thousands of flies can cause considerable damage in one orchard.

Currently olive farmers have to control the pests using traps or insecticides. But there are strict regulations on the amount of pesticide that can be used in olive groves and this is a major concern for olive oil producers.

FAO/IAEA entomologist, Andrew Jessup, explained: "Pesticides can damage the flavour of premium olive oils. There are stringent tests on the international markets for residues of pesticides and the price of the oil goes down accordingly."

He added that imported olives are also controlled by the receiving countries, and if a certain percentage of infested fruit gets through, the whole shipments of olives can be sent home or destroyed - at the cost of the exporter.

Millions of sterile flies are needed for SIT to work in the field, so the development of effective and inexpensive mass rearing technologies is the main focus of the work of the FAO/IAEA entomologists.

A further hurdle is detecting the sex of the fly before irradiation. At the moment, both sterile males and sterile females are being released. But research is being carried out at institutions in several countries including the UK and Greece to develop techniques to detect the sex of the fly in the pupal stage and to produce male-only strains.

Last update: 27 Jul 2017

Stay in touch