Photographer:Unknown Affiliation:Pest and Diseases Image Library Source:www.bugwood.org Copyright: CC BY-NC 3.0
Adult Description: Bactrocera dorsalis grows to about 8mm in length, which is larger than a house fly. The color patterns can vary; but generally a dark “T” shape on the abdomen is present or two horizontal black stripes and a longitudinal stripe extend the abdomen. The wings are clear and female possess a piercing ovipositor that allows them to deposit eggs under the skin of fruit.
Larva Description: The maggots are off-white legless and grow up to 10 mm inside the host fruit.
Host Plant: This fly has been recorded on more than 200 kinds of fruit and vegetables including: citrus, apricots, mangoes, avocado, banana, coffee, papaya, fig, coffee, passion fruit, bell pepper, grape, peach, pear, cherries, pineapple, walnut and tomato. The most commonly attacked plants are avocado, mango and papaya.
The threat of Bactrocera dorsalis is apparent. It is able to attack, infest and destroy hundreds of economically important crops in the United States. In Hawaii, maggots have been found in over 125 kinds of fruit and vegetables; causing millions of dollars in damages to the crops. Estimates for the potential effect of this fly in California range from $44-$176 million dollars in crop losses, use of pesticides and quarantine requirements. Thankfully, this fly has been continuously eradicated from the continental United States but each time it re-appears; orchards/farms along with federal and state entities, food suppliers and consumers are affected each time.
Like other fruit flies, female Bactrocera dorsalis lay eggs under the skin of fruit in groups ranging from 3 to 30 eggs. In a lifetime a single female can lay more than 1,000 eggs. Larvae (maggots) emerge from the eggs and tunnel throughout the fruit feeding on the pulp. The maggots molt two times and surface through exit holes after about 10 days. The maggots then drop from the fruit and burrow 2-3 cm into the soil to pupate and adults emerge from pupations in 10 to 12 days. Newly emerge females become sexually mature in 8 to 12 days. Adults live 90 days on average and feed on decaying fruit, plant nectar, bird feces and other substances. Adults have been observed to fly up to 30 miles in search of food and new egg-laying sites; allowing them to infest new areas quickly.
The Oriental fruit fly was thought to be introduced to Hawaii by U.S. military troops returning after World War II. Infestations started appearing in California in 1960 and have continued into 2012. As of right now though, there are no established infestations in California. In Florida, Bactrocera dorsalis, recently occurred from 1999-2010 but all populations were easily eliminated.
U.S. Habitat: Tropical to sub-tropical regions where the previously mentioned fruit, vegetable and nut crops are able to grow. Scientists are unsure as to why this fly hasn’t spread into other states like Georgia or Texas where large fruit crops are grown annually; l this fly has been managed in the continental United States.
U.S. Present: California (with repeated established infestations and eradication), Florida (easily eradicated) and Hawaii (fully established populations).
Other Bactrocera species in color pattern.
The California Department of Food and Agriculture along with the USDA have been successful in managing Bactrocera dorsalis populations through male attractant techniques. These techniques include using 600 “bait stations” within a 1.5 mile radius from each fly find for a minimum of 9-square miles. Bait stations are changed repeated every couple weeks or 1-2 lifecycles. The bait stations contain a male attractant (methyl eugenol) that is mixed with a small amount of the pesticide Dibrom (Naled). By eliminating the males, the females are unable to mate and in turn unable to reproduce which leads to the elimination of the treated populations. This technique is specific to Bactrocera dorsalis and does not cause harm to other insects.
USDA-APHIS has created a control plan for exotic fruit flies, click here for more information.
Insecticides can also help reduce populations of adults and can be applied to plants that the adults use for refuge. Also, studies have shown that in conjunction with insecticides, proper maintenance of fruit orchards; such as picking up unmarketable fruit after every harvest date, can also significantly reduce oriental fruit fly populations.
Drew, R. A., & Hancock, D. L. (1994). The Bactrocera dorsalis complex of fruit flies (Diptera: Tephritidae: Dacinae) in Asia. Bulletin of entomological research, 84(2 (SUP)).
Liquido NJ. 1991. Effect of ripeness and location of papaya fruits on the parasitization rates of Oriental fruit fly and melon fly (Diptera: Tephritidae) by braconid (Hymenoptera) parasitoids. Environmental Entomology 20: 1732-1736.
Vargas RI, Leblanc L, Putoa R, Eitam A. 2007. Impact of introduction of Bactrocera dorsalis (Diptera: Tephritidae) and classical biological control releases of Fopius arisanus (Hymenoptera: Braconidae) on economically important fruit flies in French Polynesia. Journal of Economic Entomology 100: 670-9.