How a Nuclear Technique is Helping the Dominican Republic Win the War Against the Mediterranean Fruit Fly
The Mediterranean fruit fly was reported for the first time in the Dominican Republic in March 2015. It was found in an almond tree off the coast of Punta Cana, the eastern region of the island. As soon as the government announced the presence of this pest, the United States banned the import of 18 fruits and vegetables, severely affecting the country’s main source of income after tourism: agricultural exports.
When the Ministry of Agriculture asked for assistance in March 2015, the IAEA, the FAO and other partners helped launch an eradication campaign that integrated the Sterile Insect Technique (SIT), a type of birth control for insects, to contain the outbreak of this pest.
Every week, a team of staff working under MOSCAMED-RD, the Ministry of Agriculture's programme in charge of eradicating the outbreak, receive millions of pupae of sterilized male Mediterranean fruit flies from Guatemala through the Punta Cana Airport.
These are transported in cool boxes (at 18?C) to the sterile fly packing centre. In this centre, the MOSCAMED-RD staff place the pupae into holding boxes where male flies will emerge.
They fill each box with 45 000 pupae, divided into 3 sections of 15 000 pupae each.
Each box includes a diet of sugar and cornflour spread in craft paper, and a sponge filled with water where the flies can drink from.
All boxes are stacked together and stored for five days to allow the flies to mature.
After five days, when the sterile male flies are close to sexual maturation, the boxes are taken into a refrigerated room where they are left for 45 to 60 minutes at a temperature between 0?C and 3?C.
After this time in the cold room, the flies are chilled and 'asleep', which allows the MOSCAMED-RD staff to easily collect them.
The MOSCAMED-RD team take the ‘sleepy’ flies out from their holding boxes and place them into special aerial release boxes.
The aerial release boxes are specifically designed to fit into the airplane.
A refrigerated truck (0?C - 3?C) transports the aerial boxes containing the sterile flies to the airport, where they are placed in the plane so that the chilled sterile flies can be released from it automatically through a computerized system.
The sterile flies, once released, wake up with the heat in mid-air and get ready to mate with wild female flies.
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The pilot releases them over infested areas, according to a schedule. Plans may change depending on climate conditions.
The MOSCAMED-RD programme releases 82 million sterile flies per week: 72 million by air with a plane and 10 million from the ground using vehicles.
To monitor the progress of the MOSCAMED-RD programme, the staff has established 14 525 traps throughout the country in almond, guava and caya fruit trees. Each trap contains specific attractants that can lure flies from a relatively long distance.
Every week, they inspect the traps placed in the field.
They open the traps and check if the flies in them are wild or sterile, i.e. the ones they have released. If they find more sterile flies than wild, it’s a good sign: it means the population of Mediterranean fruit flies is decreasing.
Read on to see how they tell the difference.
All the flies they find in the traps are collected and taken to the laboratory.
Once in the laboratory, they prepare each fly for identification.
So that technicians can check them under a special UV light using a microscope. Before sterilization and shipment from Guatemala, sterile flies are marked with a fluorescent colour so that technicians can distinguish them from wild flies under this light.
If the fly's head glows in the dark: bingo, it’s a sterile marked fly.
This process happens every week. The information gathered helps the team reorganize technical activities — such as adjusting the release zones — on a continuous basis.
The aim is to achieve full eradication by 2017. Once this happens, the MOSCAMED-RD team will maintain a surveillance network to be able to detect any new invasion of the Mediterranean fruit fly.
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More than 280 people are working under MOSCAMED-RD and have been trained in integrated fruit fly management, including SIT.
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Photos and text: L. Gil/IAEA
