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Mibae (Fruit Flies)


Photo: KANO Tatsuhiko

“Do you know mibae (fruit flies)?” If you ask the elderly people in Okinawa, they would probably say something like, “Oh, uri-mibae (melon flies). Their maggots eat the flesh of goya (bitter melon). In the old days, those maggots would turn the melon rotten and yellow, making it impossible to eat. It would really let us down.” Or they may say, “There weren’t many things to eat when I was a child, so my afternoon snack was the guava fruit grown in my garden. But I’d often find maggots inside. I think they were called mikan-komibae (oriental fruit fly).” If they are familiar with agriculture they would say, “I think fruit flies were eradicated thanks to the project led by the prefecture. I don’t see them anymore, it helped us a lot.”

As its Kanji name (実蝿) suggests, the small, yellow-bodied flies are harmful insects that lay their eggs inside vegetables and fruits, which develop into maggots that eat and damage the produce. The melon flies would damage bitter melons, watermelons, pumpkins as well as sweet melons, while the oriental fruit flies love citrus fruits. Mangoes, Okinawa’s recent specialty, suffered from damage caused by both species. The fruit flies didn’t originally exist in Okinawa, yet after they were found in the Yaeyama Islands in 1919, they kept traveling north, reaching as far as the Amami Islands in Kagoshima Prefecture. Not only do they harm the fruits and vegetables themselves, but farmers were troubled because they couldn’t easily ship melons and citrus fruits from Okinawa and the Amami Islands to mainland Japan. The Plant Quarantine Law restricted those melons and vegetables to the mainland, as they have the possibility of carrying fruit flies.

The Eradication Project to wipe out every single one of the flies from the islands started in Okinawa in 1972, the same year when Okinawa was returned to Japan. It was a special project started in response to the voices from the farmers, who said that if vegetables and fruits couldn’t be shipped to the mainland, the reversion would have no meaning. For the oriental fruit flies, the project placed a piece of wood, soaked in a mixture of insecticide and methyl eugenol, whose odor attract the male flies. You may have seen a small piece of wood with a metal wire dangling from a tree branch. If the males gathered around the wood piece and died, the females would lose their mating partners and soon disappear. For melon flies, they used a more intricate method. They started by artificially breeding flies, up to two hundred million every week, which were released after being exposed to radiation to make them sterile. Even if the wild flies mated with the sterile flies, they could no longer lay eggs and would eventually go extinct. The breeding site for those sterile flies still stands inside the Okinawa Prefectural Fruit Fly Eradication Project Office located in the Maji area of Naha. Both processes took quite a long time to complete, but oriental fruit flies were successfully eradicated in 1986 and melon flies in 1993.

I hope that people remember that, as a result of the Eradication Project, they can now send mangoes in the summer and tankan mandarins in the winter to their relatives and friends in mainland Japan. 

Also, it is still possible for fruit flies to reappear, as the oriental fruit flies showed up in Kume Island in 1998, before being re-eradicated thanks to people’s desperate efforts. It is still unknown how it reached Okinawa, but I truly hope that people will not carelessly bring vegetables and fruits that may have those maggots inside, allowing us to protect our products.