Oriental Fruit Fly
By Glenn I. Teves, UH CTAHR County Extension Agent
The most damaging pest of fruits in Hawaii is the Oriental Fruit Fly, a small fly about 3/16 inch in length. It arrived in Hawaii around the mid-1940s, and is a major pest of over 230 kinds of fruits and vegetables. Native to Southern Asia, it’s also found on the islands of Sri Lanka and Taiwan. In the U.S., it’s only found in Hawaii but has been intercepted in California several times. Summer is their heyday when mango, papaya, and banana are in full production, and can be distinguished from another fruit fly, the Melon Fly, by its clear wings and a black T on its abdomen.
The female Oriental Fruit Fly has a pointed abdomen or ovipositor that’s used to inject eggs into fruits and vegetables. It can lay over 130 eggs a day, and more than 1000 eggs in her 90-day lifetime. After eggs are laid in fruits, they grow into maggots or larvae that burrow through and consume fruit flesh, rotting it in the process. They complete two growth stages in the fruit, shedding their skin and exiting the fruit through the hole they were laid in as pupae. Dropping to the ground, they work their way one to two inches into the ground, where after 10 to 12 days, they grow into adults. It takes an additional 10 days before they’re sexually mature and can lay eggs. It takes one generation 37 days to complete their life cycle.
Adult flies usually feed at dawn and mate at dusk, and when not doing either, they‘re hanging out in shady areas. The adult can fly over 30 miles. A research project on Lanai successfully eradicated the Oriental Fruit Fly, but an ongoing concern was re-infestation from Maui or Molokai. To test this theory, researchers painted adult flies on Lanai and set up traps on Maui and Molokai. Unsurprisingly, painted flies were intercepted in traps along the south shore of Molokai. Their populations can explode during spring and summer months, and their ability to fly long distances and attack hundreds of different crops makes them a formidable pest. In California, the value of fruits and vegetables attacked by the Oriental Fruit Fly exceeds $10 billion, making this pest a high priority for quarantine and containment.
Many control methods are used in Hawaii. Methyl Eugenol lures on cotton balls in plastic water bottles can be hung near fruit trees to attract males. Another control option is using bait, GF 120 developed by USDA to attract and kill both males and females. GF 120 contains attractants such as proteins that mimic fruit fragrances along with an organic pesticide, and is mixed and applied to plants near susceptible crops. Another important control is sanitation, including collecting, bagging and disposing of fallen and rotted fruit so larvae cannot emerge from fruits and re-infest the area. During the mango months, this can be a major chore, but is one of the most important methods of breaking their life cycle. Since females prefer ripe fruit for egg-laying, picking fruits when not fully ripe is another control strategy.
For more information, you can download this publication from the UH College of Tropical Agriculture and Human Resources website: ctahr.hawaii.edu/oc/freepubs/pdf/IP-4.pdf.