Oriental Fruit Fly
A Potential Pest of Concern for California Farmers
The oriental fruit fly (Bactrocera dorsalis) is an invasive pest that was introduced to the US in 1946. Since then, oriental fruit fly larvae have been discovered in 632 plant taxa and of these, 481 taxa have validated records of infestation under natural field conditions. These include most of the fruit grown in California and vegetables such as bitter melon, cucumber, eggplant, peppers (sweet and hot), multiple types of pumpkins, different types of squash, tomato, watermelon, and zucchini.
Photo Credit: ecobertura.es/bactrocera-dorsalis
Why is this Pest Important?
Oriental fruit flies first made their way to California in 1960 and has subsequently been eradicated and reintroduced by the movement of infested fruit and vegetables every year since 1966. In recent times, oriental fruit flies have been found in Santa Clara, Sunnyvale, Cupertino, and San Jose.
Due to the number of crops that are susceptible to the oriental fruit fly, it has been estimated that the damage they would cause in California alone ranges from $44,000,00 to $177,000,000. Their continued presence in California also leads to increased pesticide use by both commercial and residential growers, loss of revenue due to export restrictions, and adverse impacts on native plants by the destruction of their fruit.
The oriental fruit fly is around 8 mm in length, a little larger than a housefly. They are characterized by their distinct bright yellow body that has a dark ‘T’ shaped pattern in the middle. Their wings are clear, and females have a slender, pointed ovipositor which they use to deposit eggs under the skin of the host fruit. Oriental fruit fly eggs are miniscule cylinders that are laid in batches. The larvae are a creamy-white color, and lengthwise grow as long as 10 mm in the host fruit.
Oriental Fruit Fly Life Cycle
Female fruit flies will deposit their eggs in groups of three to 30 beneath the skin of host fruits, with the potential for a single female to lay over 1,000 eggs during her lifetime. The larval development time varies based on ambient temperature. Maggots tunnel through the fruit, consuming the pulp, undergo two molts, and emerge through exit holes in approximately 10 days. Larvae fall from the fruit, burrow 2 to 3 cm into the soil for pupation, and, within 10 to 12 days, adults emerge from these puparia.
Newly emerged adult females require eight to 12 days to reach sexual maturity before beginning the egg-laying process. The breeding cycle is continuous, resulting in several annual generations. Adults, with an average lifespan of 90 days, sustain themselves by feeding on honeydew, decaying fruit, plant nectar, bird dung, and other substances. Notably, adults possess strong flying capabilities, covering distances of up to 30 miles in search of food and suitable locations for egg-laying. This long distance flying ability enables the fly to rapidly infest new areas.
Adults of the oriental fruit fly, Bactrocera dorsalis. Photo Credit: Okinawa Prefectural Fruit Fly Eradication Project Office
Damage Caused by Oriental Fruit Fly
Damage done to fruit by oriental fruit flies is caused by the larval stage. Female flies use their ovipositor to deposit eggs into ripe fruit, and the larvae feed on the pulp under the skin until they’re ready to pupate. Fruit that has been attacked is ultimately unfit for consumption, as larvae tunnel through the flesh as they feed. This allows decay organisms to enter, which leaves the interior of the fruit as a rotting mass.
A female oriental fruit fly laying eggs by inserting her ovipositor into the skin of a papaya. Photo Credit: Scott Bauer, USDA.
Ovipositor of the oriental fruit fly. Photo Credit: Okinawa Prefectural Fruit Fly Eradication Project Office.
Feeding damage caused by different stages of oriental fruit fly larvae inside an orange. Photo Credit: Unknown source.
What You Can Do
It is highly important to abide by a few USDA guidelines in order to prevent any further spread of this fly:
Do not transport or mail any fresh fruits, vegetables, or plants into California unless agricultural inspectors have cleared them first.
Know and follow all quarantine restrictions in your area. Visit the link below for a map of all active oriental fruit fly quarantine areas in California: https://cdfa.maps.arcgis.com/apps/webappviewer/index.html?id=d76b6122de514808bf89dc4438d6fb09.
Never remove fresh produce from your location or property if you are in a quarantine area.
Within the quarantine area, fruits and vegetables may be consumed or processed (juiced, frozen, cooked, or ground in the garbage disposal) at the property of origin. If not consumed or processed, double-bag fruits and vegetables in plastic bags before throwing them away.
When returning from international travel, declare all agricultural products to U.S. customs officials:
https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/the-threat/oriental-fruit-fly.
If you suspect that a fruit or vegetable in your home or at your commercial farm is affected by the oriental fruit fly, please take one of the following actions:
Contact your local county agriculture department. (Table 1 lists phone numbers.) Inform them that you wish to report a oriental fruit fly pest sighting.
Complete the California Department of Food and Agriculture (CDFA) Report a Pest Sighting Form online and submit via email to the CDFA Pest Hotline.
Report a pest by calling the CDFA Pest Hotline at 1-800-491-1899.
You can also visit www.cdfa.ca.gov/plant/fruitfly for the most up to date information on which counties are affected.